The igniter is part if the ignition system - it's the spark timing/trigger portion. Makes sense on a motorcycle since their engines don't have a lot of the stuff that car engines do. It's probably not a hall effect sensor then. Couldn't say what the output of that will be.
My project is a bicycle headlight driven by a hand-made alternator and a very small battery pack (to cover when you're stopped at a traffic light). One of my primary goals is extreme efficiency in all areas possible to reduce the load on the rider. I'm using the Arduino to control and display the alternator's output, the LED's temperature and output and the battery charging systems. Since I have so many IO pins to play with, I later decided to make it an entire dashboard with distance, speed, cadence - and now the current gear. 
http://www.chesterfamily.org/Projects/BikeGenerator/
It's sort of evolved from other projects that I wanted to improve upon.