The perfect promotional swag is this Flash 2,200 mAh Power Bank
The Flash 2,200 mAh Power Bank has a rechargeable lithium ion Grade A battery (8.14Wh) with enough power to charge smartphones, MP3 players and more. The reusable power bank charges via USB cable (included) which can recharge the battery backup or other devices with a micro-USB input like Android smartphones from Samsung®, Motorola®, HTC®, Nokia® and others. Red LED light indicates while charging. Input: 5V/800mA. Output: 5V/1000mA. Power banks are permitted in carry-on luggage only, and at the discretion of TSA agents.