Sensored motors give feedback on their position. I think that's as high res as you're gonna get, but don't know how you're going to read and intetpret that info.
Thats what systems like Traxxas telemetry does. It reads motor RPM, as well as other parameters, but, only if you have all of the corresponding parts, and a sensored motor, and, with a bluetooth link module, you can read it in real time from a smartphone. I dont have the Traxxas system, but, a friend of mine does, and, i have the FlySky IT4 that has telemetry, and it reads speed, motor RPM, temperature, and i can't remember what all else, since i havent used it in awhile, but, the IT4 displays it right on the radio itself. It can get very expensive buying all the needed parts for a telemetry system though. For example, for the Traxxas system, just to read motor RPM, you need the telemetry magnet (Traxxas part #6534), the RPM sensor (Traxxas part #6520), TQi Radio, Traxxas link module (Traxxas part #6511), the Traxxas link app, and a smart phone. To read RPM, temperature, voltage, location and speed, you need the complete Traxxas telemetry setup, and, with the GPS module, telemetry expander, and all the other needed parts, can easily cost over $300. Spektrum does it through the TM-1000 system, but, i have no experience with that one. I also know the FlySky Noble can do the same thing, and, there are many others that will as well. Do a google search for RC car telemetry, and you will find a bunch of info on it.
