I made a Transmitter/Receiver pair from a couple of PIC’s. The pair use a manchester coding system. This is a layer 2-ish solution. I put them on top of a 433 MHz rf and an IR layer 1.
I used the PICC Lite compiler from HI-TECH, which is pretty good but the version I have doesn’t handle bank switching properly.
The transmitter is a 12F675, with a 12C509 modulator for an IR data link layer or a 433 MHZ TX module from OATLEY for an RF data link layer.
Included in the source code package is the code for the 12C509 38/49 kHz IR modulator
The receiver is a 16F627 connected to an LCD display in 4 bit mode.
Look in the doc directory of the source for an explanation of the coding scheme.