[jodrellblank]

That's annoying, but it only seems to cover tap detection by accelerometer where I was thinking of tap detection by audio click, which definitely seems plausible from a quick test of the sound recorder.

Also it only covers finger swipe detection/direction determining, where I was also imagining gestures from holding fingers a few centimeters away, such as scissoring two fingers, thumb/finger flick, two finger scroll movement, two fingertips touching, etc. A quick test with the iPhone camera suggests that might have to be too carefully positioned to be practical, but should be possible at some level.