Amazon.com: Tekkeon TekCharge Mobile Power and Battery Charger: Cell Phones & Service I got two of these, one for my buddy and one for me for when we go on long rides and want to track our rides with GPS. This unit we filled with AA rechargeable batteries and it will charge the batteries and then power/charge a device.... in this case his iPhone and my mDroid. Today I used My Tracks to track our 200 mile ride PLUS I used GPS Tracker to give realtime of our location on a web page I made. I had the unit powering the droid and after over four hours, the phone was at 100% and there was still 2 out of 3 LED lights on the unit. In fact. I ran the phone down to 70% and the unit is recharging it now. They suggest running the batteries down before recharging. Great little unit. About the same width and thickness as the droid and about 3/4 tall.