Command line: GNU units - I compiled it from debian package:

http://my.arava.co.il/~matan/770/units_1.87-1_armel.deb


GUI: there is gonvert:

http://unihedron.com/projects/gonvert/index.php

This is a python program, so assuming you have python (and the necessary python modules) installed, it should work. Download the source package, open it and run from command line

python gonvert