My Wife found these on Amazon.  When water goes through the head,  it lights up and changes colors.  The kids are fascinated by it!  Check it out here.

Tantrum Tot who was officially boycotting bath time,  now loves to come sit in the tub while the colors flash and change. 

We’re not talking about flashing quickly like sirens,  but every 15-20 seconds or so it will change color.  And it brightens up the shower area while you take a shower which was the main reason my wife bought them.

They are only $40 each and they screw right on the neck of the shower without tools,  (you might need some of that white piping tape), but if I can install it,  anyone can!