Thinking about the circle pad pro and the IR port

The circle pad pro for the 3DS works through the IR port. So I was just wondering, what else can be done? Actually I was thinking it would be kinda cool if there was some kind of IR adaptor thingy that would let me use different controllers on the 3DS like an NES pad. It's an absolutely pointless level of gadgetry but it would be kinda fun to have that option!