Long time anonymous reader, first time registered contributor. 
I've been tinkering with my Arduino for a few months now after a friend had mentioned how he had to build a switch to control the signals on his model railroad and I figured I could build something using an Arduino, a Red Bear Lab Bluetooth LE shield and an iPhone to control them wirelessly. So I did. I wrote Switcher Hub Pro for iPhone 4S, 5, 5C and 5S.
The app has 12 buttons you can assign to various pin banks on the Arduino and five buttons for which you can assign actions to those buttons.
I have a little YouTube video demonstration of how the app works for the curious:
Main interface:
Assigning pins to the pin banks:
Assigning actions to the pin banks:
Changing the labels on the pin bank buttons:
Changing the labels on the action buttons: