After suffering a scaphoid fracture and doing ergo training I found it useful to get the angle measured that I can move my wrist joint - in both ways. So I designed a big enough meter that allows to measure that with one hand.

The pointer is divided, having a 90° grid, and can be changed in 2 seconds.See pics.

Update: I rounded the pointers at their base, since I realized you have to turn it for the other side of the body...