We had a chance to meet up with some of the guys from Elgato at CES 2014 and talk about Smart Key. Anyone who's prone to losing either their iPhone or their keys can deal with both problems with one app and the Smart Key.
The Smart Key works by using low power Bluetooth connectivity in order to pair your keys with your smartphone. If you come too far out of range of the Smart Key dongle, you're alerted on your iPhone. This can make the Smart Key very versatile in real world use. For example, perhaps you don't want to lose your bag that contains your MacBook and camera. Just attach the Smart Key to it and you'll be notified if it goes out of range. In case the bag is stolen, the Smart Key app shows the GPS location so you can track it down.
Since the Smart Key uses low power Bluetooth, you can expect over half a year's battery life which means one less thing to charge. If you lose or misplace your iPhone, you can do the reverse and send an audible tone to it through the Smart Key app.
The Smart Key by Elgato is available now for around $40.