Currently, I am thinking that since electromagnetic waves loose energy over distance, you might be able to figure out the relative distance to each of three radio "beacons" and use this information to triangulate the position of a Raspberry Pi robot with a radio sensor on-board.
What kind of radio receiver may I need to use, and what information about the radio signal could I use to calculate the distance to the beacon? Amplitude, perhaps? The entire system would be running indoors as an Indoor Positioning System.
In short, my question is what specific type of radio receiver would be adequate for using radio signal strength for triangulation. If amplitude contains the information of the strength of the signal, then I need a sensor that is sensitive enough to pick that up, and can provide amplitude readings in the first place.