RCON - remote connect to server?

I see many UDK-based games provide an RCON client, which allows you to login to a live server to run commands without running a copy of the game. Chivalry Medieval Warfare has one, as well as Renegade X.

Doesn’t anyone know of any open source project for this?

I’m just assuming here, but i would have anyone who has rcon tool to login as a spectator with the admin pass, so they could silently run the commands on the server.