I'd like to be able to daisy chain multiple devices using just the power supply wires and then inject a communications signal over the power lines to turn it into a half duplex network.
Are there any common methods of achieving this? The simpler the better and it would be great if it used the UART on the microcontroller.
Edit: There are actually two projects that I'm working on that I think would benefit from this – one is a low power sensor network. The other is a LED lighting project. In both cases the objective is to simplify wiring, but if the solution is too complex then it probably makes more sense to use three wires (pwr, gnd, comms).