The cheapest (and probably simplest) thing is yeah, just run two wires. If your running one, its no more difficult to run another at the same time. If you only want one wire, you could also get a hub, which will allow you to connect more devices...but at divided bandwidth...or get a switch which will be configurable to route full bandwidth as needed to different devices. It would have more ports...but if your sure you only need two devices to be wired...
Honestly, I'd just run two wires and avoid extra hardware to buy, power, configure, etc etc.