Touch R is a resistor calculator made specifically for the iPad. As a computer engineer, I hate nothing more than having to scroll to change color values to calculate resistance for a particular resistor that I'm looking for. This solves that. It's an over simplified interface that gives you the ability to focus more on your electronics project than figuring out which resistor is in your hand.
Touch R will be updated mid 2013 to include iPhone 5 support and a very very minor stability update.