RF TAG with LED ?

Hi,

I am trying to find a way to power multiple bi-color LEDs (lets call
them 'led discs') from an RF field (no batteries in 'led disc') at
close proximity to the receivers field antenna but at the same time
have these 'led discs' uniquely identifiable for the purpose of
independent control from a host system.

Control desired : led(s) on/off/flash for both anodes of the led.

So what i first thought was;

-RFID Tag CHIP (passive)
'led disc' uses a programmable RFID tag chip, which when receiving a
specific command from an RFID host receiver/controller : lights/flashes
the desired LED. Of course, the field would have to be quite powerful
and also close proximity but that is not a problem. ( i have seen many
examples flashing led's within RFID fields so i know the power at the
proximity i want is available (in bursts perhaps), but none that i can
find are independently controllable from the host system).

The problem with the above is as far as i can find, no RFID Tag chips
have any programmable functions or IO (i suppose their isnt much need?
But i have seen a few notes on people trying to do the reverse, and
make passive rfid tags which collect and send their 'sensor data', be
it a button or otherwise).

Now im looking at;
-Microchip RF series
Looking at the Microchip 'rfPIC12F675K/675F/675H' series, it appears
that these could be powered from a close proximity RF Field (operation
2 - 5 volts, very low current draw) as the controller in the 'led
disc's, plenty of program space to play with for different 'flashes'
etc, but they dont appear to both receive and transmit. But perhaps the
RF Field which is powering the device could also be serving the
signals. This is above my head here, and before i dive in, get samples
and start playing - am i even heading in the right direction here ?

Then i have started to think about other more custom solutions. Moving
away from RFID and i would love any suggestions for further research to
keep me in the right direction.

Some background info here : the led discs dont need to be bright, only
visible in ambient lighting. No batteries. Will initially be made in
low quantities. Eventually individual costs should be somewhere under
20$ in parts which i imagine is more than enough room for the parts,
and of course as small as possible :), i realise the antenna may be the
limiting factor on size.

I have been pouring over a heap of RFID chip pdf's, both for the
receivers and the tags, looking to see if there might be a way to
accomplish the above but so far have not come up with anything solid.

So any ideas ? comments, suggestions ? :)

Cheers,
Alex.

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