Good start

Nicely done so far. Not sure about the "look" but the usability is good IMO. Suggestions for additional modes: pressure, force, acceleration and torque - all with common US, Imperial and ISO units; fuel consumption (miles per gallon (US and imperial) and Litres per 100 km) and a bonus point for a concentration that also allow input of solute molecular mass ! - That should suffice for v.1.1 (:

markd5 about Units - Unit Converter for your iPhone