In the tool section in bunnings, its a little cube about 50mm x 50mm by 25mm, you can measure absolute angle or set a referance angle and then measure from that, also has a level feature and will tell you which side is up which side is down. 39 bucks
I still keep in handy the level to get rough guide straight up but then use that to get it dead eye d1ck! and its correct to the 0.1 degree aka, 32.01 deg
yay
basis is that it uses a accelorometer (i think it is) and the gravity moves some liquid or something inside (its a jesus box) and gives a output in Degrees.