It's not the most ridiculous one ever, it's just about using gesture sensing through a webcam to control Gmails interface.
The ironic thing is though this could actually be done using today's technology, I wouldn't be surprised if someone (perhaps even Google) did roll it out at some point. Apart from the gestures to type at the end of the video of course!
This is pretty funny! I always like to watch for ThinkGeek.com's April Fool's jokes every year. This year its Angry Birds Pork Rinds LoL Hooray for my first post on computer forums!