AAQR: Convertr (Utility, $0.99)

Convertr is an almost universal converter of units, from almost anything to almost anything else. Area, volume, density, force, power, length, weight, angle, and more are all possible. You can even activate / deactivate the stuff you never use. That's pretty interesting.

I don't know about paying 99 cents for it though. You can get access to that on Google easily. There are also a ton of other apps that do the same thing, albeit not as pretty, but free. So do you need this app? Maybe not.

This was give away one day on Amazon Appstore.

http://www.appbrain.com/app/convertr/com.vervv.convertr $0.99