Saw this advert - shower head with LEDs to illuminate the water stream, coulour indicates temperature.
Supposedly without batteries or external power.
"No batteries and external power supply needed. The color change tells you the water temperature. Bright LED light. Approved by CE & RoHS certificates. Electricity is generated by hydraulic mechanism."
I wonder what mecahnism they use to generate the power & if it really is as bright as the marketing pictures depict!
No doubt they will make a few dollars out of it!