Krown
Corrosion Free
Rust Check
Would be the top 3 outfits you'll see around, but any shop that uses an oily, waxy spray should be good. Keep in mind like said, this isn't a once and done thing. It's gotta be done yearly if you want it to do what it's intended to do.
If you live in the rust belt and intend to keep the vehicle as long as possible, it's a good thing to do. If you only keep your vehicles 3-5yrs and trade them in? Meh.. Hard to say.