I have one of these in my 600. It works but the magnet it was too thin and it wasn't close enough to the sensors and it was inaccurate. I had tu buy two thick magnets and put them together. Still it is difficult to have the sensors and the magnet set, a couple millimeters of difference in placement makes it inaccurate. But it can be done after many tests, but it is a pain. The neutral is not a problem as it has a reset wire that goes to the neutral sensor (you have to make it longer though, if you feed it from the dash the bike's diode makes it inaccurate).
I power it from the dash lights wire, so it reminds me that the headlights are off too (lights are mandatory where I live). I sticked the sensors with glue to the frame and the magnet sticks to the lever by itself.
I am happy with it. But it was a pain to make it work properly.
To those who think a gear indicator is unnecesary, I have to say I find it more useful than the rev clock most of times. The rev's can be guessed by the sound of the engine, but the gear can't. The speedo is definitely useless now except for radars. My bike has also a -1t front sprocket so the gears are closer and the indicator helps.