It's been tried but what do you support?
It has to do powerpoint, with the ability to do the latest version's transition effects a flash movies. People have to be able to just turn up and not need to have converted their presentation in advance
Maybe Bluetooth instead of/ in addition to USB?
If it had a well-designed, simple interface (remote control with only five or six buttons) and a high "just works" factor, it could be the Flip video camera of projectors.