Robin2:
I get the nRF24L01+ devices for about £2 each.I suspect 20m would be a long range for IR - especially if it has to compete with sunlight - but I have no direct experience. I have only tried it within a room.
...R
They're $10 each at my local store and on Canadian Amazon unfortunately. I'm only using the car indoors, so sunlight isn't too big of an issue.