iGaging AngleCube Bevel Gauge
iGaging makes a number of different measurement devices for the woodworker and carpenter, including an excellent digital protractor. This gauge provides extreme accuracy, rated at 0.2 degrees, with a resolution of 0.05 degrees. The aluminum case is backed up by magnets on three sides for ease of attachment. It will work in either relative or absolute mode, allowing you to use it as a level as well. It will measure up to 90 degrees off of any of the four sides and operates off of one 9 volt battery.