I would imagine this shouldn't be too difficult to implement. Would be great to be able to tap on an input and see a tuner. Perfect for our bass player who goes directly into the X Air.
Yes, a chromatic tuner would be very useful.
I guess the simplest way to implement it would be a new mode for the RTA utility window. There you can already affect it to any channel or solo, and it already does all the FFT you need.
A nice big display of the current note name and red arrows, green square that can be seen from the other end of the stage, and you're good to go!
I must admit that I haven't done sound for a live band in a while but I used to just throw an instance of ReaTune on the USB input for the bass player and put the plug-in on a separate monitor full-screen.
Of course, this assumes you have a DAW running during setup and sound check. Since I also used a tone generator and pink noise generator plug-in during setup that was a given for me.
Hope this helps,