I am forgetful. I have drained the batteries on my bike lights many times because I forget to turn them off. Also, I wanted to make sure I don't forget to turn the lights on in the daytime to be seen better in traffic. So, I decided to wire the switch right into the buckle. If the buckle is closed, the lights will be on.
I added metal tape to the female end of the buckle, and put the "switch" and "+" wires each on one prong on the male side. All of it needs to line up so that the metal tape completes the circuit.
To finish things nicely, I stitched the wires onto the helmet strap.