Hippih was showing off Hipkey at CES 2013. Hipkey comes as a small aluminum device that you are meant to attach to your keychain or other personal item. The device will pair up with your iPhone and then provide a digital leash for your device.
You can set it to detect between small (2-5m), medium (15-20m) and long (30-50m) distances between the devices and then trigger a sound and vibration alarm.
The free to download software seems very well designed and also offers other related functionality.
Alarm Mode: Warns you if you forget your iPhone or iPad or if someone attempts to steal it.
Child mode: Alerts you if your child wanders too far away from you.
Motion Mode: Put hipKey in your bag and you are alerted if someone moves it.
Find Me Mode: Quickly find your iPhone, iPad or your keys at any time.
It will be available on the Online Apple Store on January 15th for $89.99.