New Trent Easypak 7000mAh Portable Triple USB Port External Battery Charger/Power Pack for Smartphones, Tablets and more (w/built-in USB cable)
I have been able to go for extended bike rides and runs and I do not worry about my Iphone 4s or my Garmen Forerunner 10 going dead before finishing training runs for Ultra marathoning. It is durable and lightweight and I can't believe how much power I have available to me at any given time.