Cateye Enduro 8, hands down. They are cheap and they work great. It's not wireless, but has a thick wire ideal for off-road use. I have a few of these and love them. The one on my trance x has about 960 miles on it and is still going strong, and you know how often/badly I fall! The install is pretty easy too. Mounts well on you're fork and handlebars. That's my $.02 anyway.