What's a good battery backup for IPhone?

Question

What would be your recommended suggestion for a battery backup for an IPhone? Looking for one that has a USB port and can fully recharge the phone at least once. Preferably under $70.

Answer 1

I would suggest buying a mobile power bank like the one below. It sells cheap in ebay (just search power bank and it will give you results with different charge capacity) and I know plenty are using it.