phys.org:There's no real trick to sending out a radio signal and having a phone pick it up. That's been done before. What makes the Stick-N-Find practical is a new radio technology known as Bluetooth Low Energy, which drastically reduces the battery power needed to send out a signal. That means the disc can be small, light enough for its sticky back to adhere to a lot of surfaces, and be powered by a watch-type battery that lasts up to two years without recharging. The signal can be picked as far as 300 feet away, but that's under ideal circumstances.