Arm alarm

gtoal (instructables username) came up with a solution to avoid accidents.
After an operation, this patient was restricted by his doctor to keep his arm bellow shoulder level at all times.
This would be difficult for anyone to remember in their daily lives, and so this patient in particular developed his own solution to always be aware! It is called Arm Alarm.
To build it, one will need an anti-dozing driver alarm, also known as a nap alert (under $3), and velcro.
The device consists of a driver nap alert, which was designed to fit over the ear and buzz if you nod your head forward too much. So the innovator adapted this device to his arm. He simply glued velcro to the nap alarm and to his sleeve, in a way that it triggers when his arm raises to the maximum allowed height.

Adapted from: http://www.instructables.com/id/Arm-Alarm/