I like to use http://www.FitSW.com. It is a quick signup, completely free (I tried a few on the list but then they limit features and charge a lot to use the pro version). FitSW.com provides online tools like workout tracking & organizing, goal/body measurement progress tracking (in very nice easy to read graphs), allows you to provide demo videos for your clients and includes a scheduling system. Its made my job much easier and you can’t beat the fact that it is Free.
If you are really looking for a power tool to calculate, track, and report client progress you might want to check out http://trainermetrics.com . Not built specifically for android but can be used as a web application on any device.
Hope this helped,