The Tethercell Gives Remote Access to AA battery Powered Electronics

Using your smartphone and a Tethercell you can now control whether a AA battery powered device is on or off by using the Tetherboard app on your smartphone. You just put a AAA battery into this AA sized cell case and then put these into any electronics that use AA batteries. It even alerts your smartphone when the batteries are running low!

Source: http://ces.cnet.com/8301-34441_1-57562664/tethercell-magically-turns-aa-batteries-into-bluetooth-devices/