I wouldn't feel secure enough to use something like that. 1) it's a collar, even breakaways aren't 100% safe. (see a
recent thread of a cat that got out in a collar

)
And 2) I've read reviews for a few of these collars. A lot of people complain of cats drooling, losing fur (this can simply be from a reaction to plastic that some cats have), and some cats acting "stoned" and lethargic from the stuff they imbed in the collar.
Other people complain about how strongly scented the collars are and that it bothers them.
IMO, go with the feliway diffusers and spray.