Re: generating electricity in a shower-head
At 5 volts, not very much.
If you want something properly scary, try using an electric shower in Central or South America - a.k.a. "suicide shower". They consist of a shower head with in-built heating element; the live/neutral wires connect directly to it, usually via a terminal block with some tape wrapped around.
They are mainly made in Brazil, and examples are easy to find online.
Biting the hand that feeds IT
