Do your customers fear running out of mobile device power at the wort possible time? Proporta suggests the TurboCharger Pocket Power for such emergencies-- a charger small enough to fit in a wallet.
The Pocket Power measures 90 x 54 x 7mm and "packs a surprisingly high amount of power" according to the company. It has 680mAh capacity, and Proporta claims the Pocket Power can charge a Samsung Galaxy S3 by 23%, a Kindle 4 by 50%, an iPhone 4S by 34% and the Google Nexus 7 by 11%.
Charging comes through micro USB port (with an adapter for Apple devices). LED lights indicate the amount of charge left.