Let's Make Robots!

My first robot: Any ideas on how to do this?

Hey everybody, this is my first post here. I'll be ordering the parts to make my first robot soon (within a week, hopefully), and I've had lots of ideas. I've had some experience building robots, but not real ones; only ones with Wiremod in Garry's Mod (A really fun modification of the Half-Life 2 source engine). I'm planning on making it be able to track an object (a transmitter) using 2 receivers that can measure signal strength and output it as a distance. Any ideas of what I can use for this? It'd need to be pretty accurate within 50 feet or so.