In an attempt to figure out the revs on Salty, I picked up a cheap little tachometer from Prohoists. It is self-powered, and pretty darn easy to install. The pickup signal wire wraps around the main coil lead, and ground wire mounts to a chassis ground. The end.
And it works. I've heard I might need to play with how many times the signal wire wraps around the coil wire, but so far it seems to work. It might reading a tad high, but I want to borrow the wireless tach from work to compare the two before getting it dialed in.
I built a quick little aluminum mount that attaches to the steering stem. I still need to pickup a couple small bolts to mount the unit to the bracket I built.