The original Smackbook was the nickname give to combination of software that allowed desktop switch by 'smacking' the Mac.
It worked by enabling virtual desktops via Desktop Manager, the AMS sensor (to read the Hard drives sudden motion sensor), and a small script to pass info between the two forcing the switch - all a bit of hack. 😛
Time has moved on and if you want to play it's now easier to just download Virtual Desktops, as it's got built in support for motion sensor