I use a Sigma model (BC906, $30) that has been discontinued, but their Web site
http://www.sigmasport.com/en/produkte/bikecomputer/ shows several candidates. You want a wired model. Like DrunkenDwarf says above, make sure your choice can handle high speeds.
I mounted my display on the center of the handlebars. The sender is a small metal disc, strongly magnetic, that I mounted on front brake rotor (used a small drop of glue for back-up). I used zip ties to mount the small receiver on the left front fork tube.
I calibrated it by measuring the distance travelled by the front tire in two revolutions, divided by 2, and entered that into the computer (wheel size). It's dead accurate according to the roadside you-are-going-this-fast-according-to-police-radar displays. The stock speedo reads 3-5 mph higher than this bike computer.
There's no illumination, but I rarely ride at night, so it's not an issue for me. Anyways fiddling with it to make it light up would defeat the purpose of helping keep my eyes on the road. I suppose you could rig an LED to illuminate it off the stock speedo light if it were important.
It has a speedometer, odometer, total engine hours, trip hours, trip distance, time of day, trip avg speed, max speed (mine reads 77.88 mph). When my trip distance hits 100 it's time to look for gas.
Entire installation and calibration took about an hour. If you do a Search on All Posts on this forum you'll find photos of other installs. That's how I got started.
For example,
http://suzukisavage.com/cgi-bin/YaBB.pl?board=tech;action=display;num=1183653316