Well, okay guys, I'll give you a "solution" since this is proposing to use RF anyway. Instead of doing it entirely wirelessly use a very thin conductor surface wave transmission line (SWTL). That way only one conductor is needed and the RF energy is mostly contained within a wavelength or so of the SWTL (think "inside-out waveguide). The conductor can be very thin, like 28 awg. Or, for spanning larger distance, SWTL mode has been demonstrated on twisted aluminum cord used in normal power lines. It's just a matter of adapting the coaxial to SWTL launcher (sort of cone).