You think that CHDK get access to the motion detector that is in the camera ?
im fairly shure that it could.....
Most people dont even know that the PowerShot 300HS has this.....
to prove it Let your camera fall to sleep and then wiggle it to wake it up.
OR
just like when you view your pictures on the camera turn the camera on its side and watch what happens..
now i feel that if i can get access to this in the camera there could be some More cool scripts made up for it.
I Do know...........
if you can control some of the Hardware of the camera with Chdk like you can this shuld be Just as easy as usen the Manual Focus or turning the ND filter on or off.