Here is a cool little app called mtoolbox from [germany]merlot over at XDA. This app uses several of the phones built in sensors to give you variety of tools like a light sensor, ruler, level and angle meter, and a shock sensor. I have actually used the level sensor a lot in my research lab to make sure that the level of my gel is even because people don’t put the real levels where they are supposed to be.

The app is available for all the different screen resolutions including VGA, WVGA, and QVGA. Click here for the XDA thread or here to go directly to the download site.  Give the app a try or just leave it on your phone. You never know when you might need to get an approximate length of something or when you might want to measure the seismic activity of an earth quake :)