> I've got a project on the backburner that would involve a flat disk 
> with
> embedded murcury tilt-sensors and solar-cells to run everything. I'd
> throw in a bunch of super-capacitors for night operation. Just gotta
> find a way to get sufficient power, it'd need a radio link to
> communicate with a similar module inside, and super-capacitors just
> don't store much energy.

Inductive power transfer.
Essentially two transformer halves.
Resonating the receiving side allows quite magical separations.

Photocells (as you've noted).
You could cheat and drive them with IR at night.

Mechanical movement to drive an internal alternator (eg rock it to and 
fro or shake it :-)  )

Ultrasonics.

...


        RM


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