We don't normally look to shower radios for technological advances, but this one manages to power itself with a micro-turbine generator that runs off of the water flowing through your pipes.
"Micro-turbine generator" possibly sounds a little bit cooler than what it actually is, which is just a wheel that spins in flowing water to generate electricity. Basically, it's like the Hoover Dam, except smaller and in a shower radio. You attach it in between your pipes and your shower head, and as the water flows in your tunes flow out.
While to some extent your water company is paying to run this shower radio via the water pressure that they provide, there's going to be a corresponding reduction in your shower's strength whenever you have this thing hooked up. You might not notice, but if you do, just think of it as a subtle and friendly reminder of the first law of thermodynamics: even free power is never really free.
The H2O Shower Power Radio is available this month for about $56.