Here's a unique unit converter for the iPhone.
As far as I can tell, this is the only units app that allows you to choose arbitrary pair of units and save them as favorites. Put km/h to mph, km to mi, Fahrenheit to Celsius on one screen, easy to access any time.
It also has instant search for any unit.
Take a look at the videos and screenshots for more: http://radianttap.com/units/
Direct link to store: http://itunes.apple.com/app/id717659011?at=11l8s2&ct=macrumors
As far as I can tell, this is the only units app that allows you to choose arbitrary pair of units and save them as favorites. Put km/h to mph, km to mi, Fahrenheit to Celsius on one screen, easy to access any time.
It also has instant search for any unit.
Take a look at the videos and screenshots for more: http://radianttap.com/units/
Direct link to store: http://itunes.apple.com/app/id717659011?at=11l8s2&ct=macrumors