hi nightlight....are you talking about intonation or tuning? they differ a lot.
intonation to me is when we test our fretted note at 12th fret to be exactly as the free sounding string (one octave lower though). tuning is cheching that the strings are in tune.
in the intonation phase there was no way to check with surgical precision if the 12th fret note was precisely as it should have been. I have a superb ear (not absolute one) and I always test the intonation by playing the harmonic at the 12th fret and immediately after the fretted note at the same fret. well, you can hear differences if any but when the intonation is getting closer, I found no way to tell if there was a difference. instead, checking on the strobe tuner there was a difference even minimal which tended to get worst as I fretted notes towards the 24th fret. so I guess for intonation there is no room for approximation.
but that is just me....
michael
Intonation, which is why I mentioned having the 12th fret harmonic sound the same as the fretted note at the 12th fret. I'm not aware of tuners that help you do this, since I do this process on my guitars by ears to ensure that they have the same pitch, which means that there will be no dissonance when playing chords or even at various frets on different strings.
I was talking about intonation and tuners because that was the thread topic. I have no idea whether tuners can help with this, as mentioned.