How much accuracy can I get with RF / acoustic triangulation?
If you are considering using this in a room, I suggest you avoid RF and go acoustic. RF travels about 11 inches each nanosecond, so you would need to be able to synchronize time measurements down to nanoseconds (and the cables to the sensors would be an ingredient in the measurement).

Sound, on the other hand, travels about 13 inches per millisecond. You can get millimeter accuracy with a simple microcontroller with timers. Also, cable lengths will become insignificant.

Put a piezo transducer on the object that you wish to track. A short ultrasonic burst a few times each second would be all you need. Something like a 40 kHz tone, lasting 1 millisecond, repeated every 50 millisecond (that will cover a 50 foot sphere). Put a bandpass filter with discriminator for each sensor, and then trigger timers at the leading edge of each burst. The time delta between the received pulses would allow you to triangulate the 3D position (for 3D space, you would need a minimum of 4 sensors).