If you have established the communication with a RS232 wired link, then I dont think that going wireless is not that big an issue - mainly because you dont want a big range - you say its only inside a room. Maybe about 20 to 30 Meters would be OK ?

I would suggest that you try transmission over an FM radio link with one of the commercially available 433Mhz Transciever modules sets. The net is full of such references and these are available as hybrid modules. The advantage with this frequency is that it is allowed in most countries, with limited transmitting powers. OK members might have plenty of comments / tips on this aspect.

Quite some time back I have used this approach for a remote controlled tractor.

Raghu