Neat. I think it's a reasonable idea + quest or experiment.
They make some backpacks (for nerds) that have a smaller solar panel than yours, and they imply it can trickle charge a phone, ipad, etc, certainly with the proper cord at the other end to the actual device.
As an experiment, it might be interesting to start out by isolating the output (to just one device instead of the overall bike) by hooking it to a pretty dead or discharged smart phone, and then head out on a ride, with just the phone connected to your panel, and see an hour later, and then an hour or so after that at what point the phone is charged.
It would at least be an example of it's capabilities for something most people could wrap their mind around, granted it's not totally scientific.
Again, I think it's a neat idea, and those panels are sometimes quite reasonably priced. It would be interesting to play with.