TNC from Skyborne..
I can tell you a little about the TNC from Skyborne...
Works great, so much more sensitive than the Futaba tach I was using. Don't have to even get close to the prop to get a reading, I just lay it on the ground behind the prop so I can hold the plane and tune without even touching the tach. You have to press a button to get the high res reading, but by that time I'm not fiddling with the needle.