The most common use of wireless energy transfer today is in RFID tags. These are the things that you commonly find in Music Stores and Libraries. When they pass through the detectors (which produce a rf signal), the signal induces power in the tag allowing the chip to power up and transmit a response. These tags do not have any battery backup and rely entirely on self-generated power.
Long distance transmission of wireless energy has been limited to microwave frequencies which has raised potential health risks and has therefore not been implemented.
At the 2007 Consumer Electronics Show a new company called ‘Powercast’ demonstrated some devices that won them, ‘best emerging technology’, but all of these were limited to a few metres and involved 'trickle charging'.
Current technology can't even charge a laptop at a distance
but they can manage a toothbrush
Now with regard to R/C
Let’s assume that a race track is 20m x 20m and the power source is situated in the centre – this means that it has to be capable of generating power over a 10m radius.
At peak discharge let’s assume that a motor will draw 30A. 30A x 7.2v = 216W
So if the car was immediately next to the power source 216W would be sufficient. But the car might be 10m away from the source so by applying the inverse square law it would need 100x this power = 21600W = 21.6KW. Now there are 10 cars on the track and each one needs its own fix so that is now 216KW
216KW is serious power!
My stand-by generator for power cuts at home is rated at 1.2KW - makes a lot of noise and consumes petrol at an alarming rate! I can't imagine a unit 180 times as big capable of producing 216KW in the middle of your track!