Haha sorry I didn't do a very good job of explaining myself. A robot will be driven into a "slot" and the transmitter will be on the bottom of the robot, the reader being under the robot. Only one robot will be in each slot at a time, but there will be multiple slots. This is the only point that the data will be sent.
In that case, IR would probably be the simplest to implement - but another possibility might be an air-gap transformer (1:1 ratio) system, with half of the "transformer" on the robot, and half under the slot. It's something to think about, but an IR system would likely be easier and cheaper (not too mention easier to align and "tune").