Making fall detection, help with accelerometer.

Hi,

I'm trying to create a system for fall detection for my watch app. My idea was to simply check in a method that updates every second if there was a large change in the x, y, and z values of the accelerometer, but I'm not sure this is the way to go. Milli-G's are force I think so maybe it's not a change in x,y,z as much as it is a very large number? I'm sorry for my lack of knowledge of physics, haven't taken it yet. If someone could point me in the right direction I'd really appreciate it.