RF + no wired connection to laptop + laptop + cheap-ass receiver = impossible it's something as insidious as a GPS tracker, keylogger, or any real nefarious device, really.
It's probably something retarded, like an RF receiver for a DVD remote control. In fact, that's probably exactly what that is. Unfortunately, Google searches on the part number are useless, comes up as an LCD inverter board. I'd call Apple, give them the model number, ask them if there was an option for it to come with a remote - I can guarantee you it was an add-on option for the laptop, and would explain why it's not an official Apple product, as I would expect that to be an outsourced job.