Resimho is a very simple to use resistor value calculator App available for Android. Resimho has been tested on an Android 2.2 device and should work seamlessly for any higher versions.
Simply select the 4 different colours found on the resistor and the app will calculate the resistance. Not much, but, it does come in handy when you're in the workshop creating something and happened to have forgotten the colour code values.
Available free on Google Play: Link