There have been a handful of iOS gaming controllers released since Apple added MFi controller support to iOS 7, but most cost between $80 to $100 and require a Lightning connection to work. Logitech's PowerShell was originally one of those $100 iPhone controllers, but it is now available for only $50 on Amazon.com.
The Logitech PowerShell easily attaches to the iPhone 5, 5s and fifth-generation iPod running iOS 7.0 or later. It is equipped with a 1500 mAh battery, an analog directional pad, and several buttons including two shoulder trigger buttons. Logitech promises the controller "fits easily into your pocket" thanks to its "portable slim, streamlined" design.