Wallet sensor in its "final form." (via hack-a-day http://hackaday.com/2013/03/08/quick-wallet-hack-adds-pickpocket-alarm/)
Caleb Craft was searching the web when he noticed references to a small group of people who can pickpocket just about anybody. Being the clever hacker he is, he decided to integrate an alarm into a wallet that would sound off if someone ever tried to swipe it. There are currently solutions to this problem already available, however, and as Caleb points out most of the wallet alarms available will not go off until light hits the device. If a pickpocket swipes your wallet and does not open it right away, the alarm would be useless. This is where Caleb used his ingenuity to create a better solution.
Finding a small magnetic window alarm Caleb quickly went to work on how to incorporate it into a wallet. The original alarm works using a buzzer and magnetic reed switch. The reed switch works by an applied magnetic field which in turn, opens or closes a switch. Furthermore, Caleb decided all he would need to change on the alarm would be the thickness of the design. Leaving the casing around the buzzer, which acts as an amplifier for it, the reed switch was de-soldered and moved to the side of the unit. This allowed the design to slim down just enough to make it unnoticeable while the wallet sits in your back pocket. The switch was placed in the wallet towards the spine and is easily accessible for the user to reach. His hack included using hot glue to secure the alarm to the wallet and a small magnet that gets secured in the back pocket.
Caleb's design worked as planned and fit comfortably in his pocket without any unusual bulkiness. When the wallet is removed the alarm continuously goes off and would probably scare any thief into dropping the alarming wallet. Caleb states that the only improvement he would suggest for anyone would be a stronger magnet so the wallet would not need to be aligned perfectly in the pocket. If any thief decides to try to swipe Caleb's wallet, they could be sure they are in for an unusual surprise.
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