InputDevice provides data (i2c sensor, temperature sensor, mouse, camera, mic, voltage meter) computer responds to said data stream. It's kinda what they do.
Hell, if you count the optic sensors as primitive cameras you can extend the analogy.
Like I said before, I have no problems on copyrighting code, or patenting a specific way to determine motion in a specific context... but the arbitrary gesture parts are where things get hinky, starting at Claim 11.
The guy who wrote motion was doing the same thing... he was just making it easier for other folks.
I didn't have time to read the whole page, but I know for certain that he was operational in 2009 as I was hoping that he would have time to work out the kinks to make things a bit more stable.