I put Hardline Hour Meters (inductive type) on all three of our ATVs. I'm not sure they qualify as "good", but they count running time OK. They have a single wire that wraps around the spark plug wire 5 or 6 times, and a self-contained battery that keeps the display on all the time. They are attached with double-sided tape and a couple of screws.
I have no idea how long they may last. The display and electronics are sealed, and the battery is not replaceable. It's an easy install, however.
You can do a search on eBay and find prices all over the place.