This was the most entertaining idea at DemoFall so far, and probably the most ridiculous: MixGet (site not live yet). It's technology that turns individual cellphones into synchronized music players. So if you have a crowd of people together, one person's phone might play a guitar track, another vocals, another drums.
The presenter tried to justify this product as a potential new kind of ringtone, but I'm not sure I see it. This project is from Redsquare Ventures, which is trying to bring Russian entrepreneurs' ideas to market.
I love this idea. But I don't see the market.