Bluetooth Low Energy (BLE) is one of the overlooked heroes of iOS. Part of Bluetooth 4.0, it offers a low-power way to wirelessly connect sensors and other short-range devices to applications that can, with Apple's blessing, run in the background. That means, your phone can track and monitor systems without you having to keep an application open full-time and it won't run down your battery.
Still an emerging technology, lots of BLE projects are just ramping up. I recently had a chance to try out a prototype of Phone Halo's Wallet TrackR system. Small enough to fit in your wallet, the Wallet TrackR uses BLE to virtually tether valuables to your iPhone.
It works like this. You slide the trac
