Review on Digital Protractor DXL360S Inclinometer 0 01°Resolution by Tony Wilson

Not only is it a good 2-axis spirit level (i.e. replacement for a round spirit level) and inclinometer, but it can also make fairly accurate horizontal rotation measurements. For example, you can measure an angle in a corner of a room. The accuracy is about 1-1.5 degrees; slightly better when moving very slowly (10 seconds, which seems like an eternity but isn't really that long)