Stick2Can is a walking cane for people with a balance disabilities who only use a cane during an episode that can physically walk away from the cane before they actually need it. The user attaches a transmitter to the cane, and carries a receiver that beeps/vibrates/etc. when it's out of range.
Use a 433/415MHz kit (MX-FS-03V/MX-05V or similar) transmitter. The patient carries the receiver (+ arduino + buzzer/vibrator) in their pocket or bag. The transmitter is attached to the walking cane (only a 555-based oscillatorr). The transmitter is attached to the cane with an elastic bandage. On the receiver side, there would be a really small arduino-based "appliance" (i.e. comes pre-programmed). To reprogram it, use a Future Technology Devices International (FTDI) Cable.
For more detailed instructions: http://www.instructables.com/id/Stick2Cane-never-lose-your-walking-cane/
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