If I were to use (strong rare earth) magnets as the cores, would that
significantly increase power transfer ? I've recently discovered an
application where transfer of 20-30mA (@ 4-ish volts, ~100mW)
across about 6mm of air would be just super. Or is permanent
magnetism a no-no ?

I've noticed that some of the inductors/coils I've pulled from boards
are wound on magnets, whilst some are magnetic (presumably soft
iron like power transformer cores) and others are ferrite

Reading pages like this to get some ideas

http://en.wikipedia.org/wiki/Resonant_inductive_coupling

Not too worried about efficiency. The primary could be driven to
any necessarily high voltage at high frequency with an SMPS IC
--=20
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