I was talking with Steve Lee about the lack of tactile feedback in our simple video switch. We could play an audio click or even vibrate something like one of the haptic mice that were popular a few years ago. For many users making the switch target tactually interesting will be important.
Another possibility would be using some sort of cheap clicker in place of the switch. I'm thinking of those novelty toys we used to get in Cracker Jacks, or something comparably cheap. I think the sound of an appropriately chosen clicker should be easy to detect with a microphone and simple signal processing. The advantage of this arrangement is that the user and the computer know exactly when the switch selection happened and the video distinguishes which switch selection happened.