Here's what I've heard on the topic. I'm no expert.
However, if the employee is educated, trained, etc., you will have a hard time enforcing any kind of non-compete; the guy has to earn a living. The courts will not look kindly on a company trying to prohibit a guy from finding employment in the feild he has prior training/education in.
I wish I could quote the articles I read on this, but it's been awhile.
If he's just a pair of arms, I don't know if a non-compete is worth your effort.