The Goblin: Magnetic Motion Detector.
The Goblin is an iOS app inspired by retro dark fantasy video games. An era when the simplest arrangements of pixels conjured the deepest chills and the most lasting myths.
The app takes full advantage of your phone’s built-in magnetometer, in a way never seen or used before in magic and mentalism. Unlike most magnet detectors available today, The Goblin is not a proximity sensor, but instead relies on motion in the magnetic field.
Most magnet detectors trigger when a magnet comes within range, usually alerting the performer with vibration or sound. While phones can detect magnets too, they must be brought very close to the source, which isn’t practical in a performance environment. Increasing the phone’s sensitivity extends the range, but this often results in constant false readings from other magnetic activity in the room.
The Goblin works differently. It uses sophisticated behavior modeling to act less like a rigid sensor and more like a living system. When activated, it learns the surrounding magnetic environment and continues to adapt, allowing it to ignore background movement that you or your participant did not cause.
Rather than reacting to proximity alone, The Goblin responds to sudden motion and spikes within the magnetic field.
Every magnet is surrounded by a magnetic field. Stronger magnets have larger fields. If a magnet is too far away, its movement blends into background activity and is ignored. When a magnet moves closer, its motion creates a clearer spike in the field, which The Goblin can detect.
To test a magnetic prop, activate The Goblin and place your phone on a table. Step back and move the magnet. If there is no response, move slightly closer and try again until detection occurs. This tells you how close that prop needs to be to trigger The Goblin.
Only a sudden change is required. Continuous motion or getting even closer to your phone is not necessary. A quick pass of a magnet near the phone is enough to trigger a response.
Let’s say, The Goblin is in “hunt” mode and your phone is in your right trouser pocket.
Hand a magnetic item, such as a coin or poker chip with a hidden magnet inside it, to your participant and ask them to mix it between their hands behind their back. Once done, they should relax and place their hands by their sides, with both hands making a fist (the magnetic item is hidden in either fist).
Now, if you ask your participant to raise their left fist out in front of them, they will be bringing their hand up and past your right pocket where your phone is. It doesn’t matter if they move fast or slow, the magnet simply needs to pass through The Goblin’s territory.
If you feel no response from The Goblin, that hand must be empty, and so the magnetic item will be in their right hand.
If you feel a response from The Goblin, then of course this hand, their left hand, must contain the magnetic item.
As an alternative, your phone could be placed in an inside jacket pocket, so that your participant’s hand ends up even closer to The Goblin’s territory. This is ideal for props or items that have a weaker magnet inside them.
Another option is to stand beside your participant while their hands are resting by their sides. In this position, you will be stood directly beside them, while you both face the audience. This gives you an excuse to bring your trouser pocket, The Goblin’s territory, closer to their resting hand, without feeling as though you’re uncomfortably close to them. Then, when you ask them to raise that hand in front of them, or even raise it to their chest, they will be moving away from the territory, which will trigger The Goblin, if that’s the hand concealing the item. If there’s no response, the item must be in their other hand.
Which Hand.
Let’s say that you have three poker chips. Two red ones that are standard, and a green one that contains a magnet.
Ask your participant to hold out their hand, and step closer to them as you place the three chips, one by one, into their hand. As you place the chips, try to feel for a response from The Goblin as you place the magnetic chip down. If you feel no response, subtly reposition their hand, or re-arrange the order of the chips until you do get a response. That way, you’ll know that the magnetic chip is now in The Goblin’s territory.
Say to your participant, “In a moment, I will close my eyes. When my eyes are closed, keep your hand here, but with your other hand, pick up any one of the chips, but don’t tell me which one you’ve taken. Once you’ve chosen one, put it straight into your pocket.”
Then, close your eyes and ask your participant to remove a poker chip. If The Goblin responds, they took the green chip. If there’s no response, they took a red chip.
Once they have confirmed that the action is done, keep your eyes closed and ask them to take another chip, and hold it in their fist. Again, Goblin response or no response will inform you which colour chip they took.
Once done, say, “and finally, close your hand around the last chip, so that when I open my eyes, you will have one chip in each fist, and one in your pocket, and I won’t know which colours are where.”
Of course, you will know which chip is where, because of The Goblin. If you feel a response the first time, your magnetic chip is in their pocket. If you feel it the second time, you know it’s in their hand, and if you don’t feel any responses, the magnetic chip still sits in their outstretched hand. You can even ask them to move their final hand when your eyes are open, just to check for a response from The Goblin, for further confirmation.
From here, you can “sense” and reveal where the red chips are, and where the target, green chip, ended up.
Which Hand 3 Items.
This is great for items containing magnets that are too weak to sense from any sort of distance.
Borrowing from the example above with the three chips, you could explain that if you held the three items in your hand and asked them to take one, you’d be able to feel which one they took, but if you placed the items on a flat surface, such as your phone, you wouldn’t be able to feel their selection.
Now, you can hold out your phone like a little table and place the three items on the screen.
With the Footsteps (Haptics) option, and Stealth mode active, your phone screen will stay black for the duration of the performance, and you’ll be able to feel the Haptic response when the magnetic item has been taken away.
Easy Items.
A simple variation of Max Maven’s classic. Let’s say, you have four white balls and one black ball which contains a magnet, all mixed up in a large velvet bag.
Members of the audience are invited to reach inside the bag and remove a ball, concealing their choice so that you do not know who has the black ball.
After each selection, all you have to do while holding the bag and standing still for a moment, is casually allow the bag to move through The Goblin’s territory, past your trouser pocket. If the magnetic ball is still inside the bag, The Goblin will respond. Once the magnetic ball has been taken from the bag, you’ll feel no further responses, and this way, you’ll know who’s holding the black ball.
Kurotsuke.
Take an old, hardback book and cut a rectangle out of a large portion of the pages in the middle, enough to conceal your phone inside. The book cover can be opened and the first few pages shown without anyone knowing that there’s a phone hidden inside it. Using the book as a tray, you can place your magnetic and non-magnetic items on top. When the magnetic item is taken, you will feel the haptics or vibration through the book.
If you take a wide bowl and place a decorative cloth inside, your phone can be hidden under the cloth. The items would then be placed inside the bowl, and when the magnetic item is taken, again, you’ll feel The Goblin’s response through the bowl.
When using a PeekSmith device, The Goblin’s response can be set to silent, so that there’s no haptics or vibration. Instead, when The Goblin is triggered, your PeekSmith will notify you. PeekSmith vibration can also be enabled via the app, so if you cannot see your PeekSmith screen, you will still feel the response.
This allows you to hide your phone in a book, bowl, box or other, then walk away from it. Completely hands off, and even blindfolded, you will know the exact moment your magnetic item is moved or taken, via your PeekSmith.
Book and Bowl.
Wooden tarot boxes can be acquired easily and inexpensively online or in New Age shops. They’re often small wooden boxes with a hinged lid, big enough to fit a full tarot deck.
In mine I keep the 22 major arcana, which leaves more than enough room for my phone, a pendulum in a small velvet bag, some billets, a sharpie and some coins. There are four old English pennies and one magnetic half dollar. The tarot cards, billets and sharpie are used for other routines, but the coins and pendulum are used with The Goblin.
No matter what’s in the box, my phone sits beneath everything (the tarot cards help to cover it in case anybody sees inside the box). Inside the velvet bag with the pendulum, there’s also a PeekSmith.
With the PeekSmith on and The Goblin in Stealth mode with Silence enabled, I’m ready to begin.
The five coins and pendulum bag are removed from the box. The box is closed, and the coins are shown one by one and placed on top of the box.
I then remove the pendulum from the little bag, briefly explain what it is, then casually hold both the pendulum and the bag containing the PeekSmith in one hand, freeing up my other hand to gesture towards volunteers and the coins.
Five participants or volunteers are chosen to come and choose a coin, then stand behind me one by one, forming a line. With the box and coins behind me too, I can continue to face the audience during the selection process.
By selecting participants one by one, and ensuring that only one person at a time is choosing a coin then standing in line, I will know exactly who takes the half dollar, the odd one out, because the PeekSmith hidden in the bag in my hand will vibrate.
Once all coins have been chosen, it’s time to use the pendulum. I simply hold it up with one hand, then pocket the bag (and PeekSmith) with my other hand.
Now I’m completely clean, and I know who’s holding the half dollar before we’ve even begun. From here, I can do as I wish with the pendulum to locate the coin. I could hold it above their hands one by one and force the pendulum to behave differently when I get to the hand containing the half dollar, or stand in one place asking my participants questions, then observing the pendulum’s movements as though it is somehow assisting me.
A quick tip: ensure that your magnetic item won’t stick to your non-magnetic items.
Some possible combinations:
Five coins of one denomination, a magnetic coin of a different denomination.
Four poker chips or dice of one colour, with a magnetic chip or die of a different colour.
Four crystals and one stone (a magnet concealed in a lump of air-dry clay and painted black or grey to look like a stone).
Four identical, opaque drawstring bags, one with a magnet concealed inside it. Then, any items can be placed inside, even if they have no magnetic properties.
