If there is something tat every mobile phone is used for while out and about, apart from making calls, it is performing calculations and conversions. Ordinarily, this might involve using two different applications; one to perform the conversion and another to perform a calculation based on the results.
Using Convert ~ the unit calculator for iPhone, both of these options are available in the same app. All of the units you would expect can be found here - energy, currency, time, speed, temperature, etc - and the simple, elegant interface, converting between units is a breeze.
A simple dial interface is used to provide access to the different units, and the calculator keypad is used to enter unit values. Conversion itself is quick and simple, but the inclusion of a calculator option is a real bonus.
The calculator can be used for many things, but is comes in particularly handy when working from a recipe when you need to increase or decrease quantities. If you regular convert between certain units, they can be added as favourites for easy access. A wonderful designed, well thought out and useful app.