This is pretty cool -- it's a bike-mounted iPad-controlled stereo spotted at a recent meetup for a group of BMX riders. There's not a lot of information on how it was all put together (maybe if user Mikey Wally sees this, he can tell us more in the comments below), but it looks like the iPad is secured with a handlebars mount, and then it's plugged into a speaker that's stuck on the front. Assuming it is secure (and I hope it is, otherwise you're going to have a very broken iPad), it seems like a pretty wild way to make your music mobile. As we've discussed before, having an iPad on a bike can be handy in certain situations.
I think it'd be cool to see another music app running on there, or maybe even hook the iPad's accelerometer to the bike somehow, and have it display trip information of some kind as you traveled.