Two tools in one: a level and it also shows the current the gravity unit and record the gravity. The level also provides the tilt angle and measures angles by using saved angle feature.
To buy use zune://navigate/?appID=f31e42f2-7c0d-e011-9264-00237de2db9e
or search "aPanaSoft" in the market place on your phone.
Find more apps from aPanaSoft at aPanaSoft, or follow aPanaSoft on twitter.