They display inlet temp, coolant temp, rpm, boost, voltage, and you can run water injection off it too i believe but i haven't got mine wired up.
Not sure about connection it up to an RST, BUT i guess if you figure out exactly how it works you coud probably do it somehow. But I'm not really qualified to answer that I'm afraid.
Really happy i got mine as I've had a few issues and it really helped me out, for example i had a recurring missfire, i couldn't figure it out, but it turned out the ECU was seeing double RPM and it was the rev limiter cutting in thinking it was at 7500rpm, but it didn't show that on the dash rev counter, but it did on the SECS display.