You all might be interested in this info.  www.kisantech.com has headlamp
modulators and they claim to use a P-channel mosfet using current regulation
for the modulation.  150 watts maximum.  It's a very small package that
modulates current between 100% and 13% (I guess so the filament doesn't cool
too much)  It also has a light sensor to deactivate the modulation upon
entering a tunnel or darkness.  Pretty neat product, but cost's way too
much. $100.00 for single bulb setup.

You might also be interested in the tireAlert pressure monitoring system.
Uses unpowered device that is attached to the wheel to sense tire pressure.
They claim 1 psi accuracy.  I think that you would have to have the tires
rebalanced after installation.

Any ideas on how the unpowered sending unit functions?  I'm guessing some
kind of internal coil or LC resonant tank.

There's a pretty good market for these kinds of "gadgets".  Bikers love to
spend money on bike toys.  Toys that help you to be seen are very popular.

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