Yep! I've used them to treat insect mites.
If you have LARGE reptile mites (the black ones about 3mm across) they won't do you any good. If you have those, do a google search for the product "Provent-A-Mite", this stuff is safe for reptiles, simple to use, and totally eradicates mites if you follow the directions. I can't recommend it highly enough.
The predatory mites that can be used for teenytiny microscopic mites are called Hypoaspis sp. mites. You're right that they feed on other mites (and plant matter) and only live a couple of weeks and then die out.
You can buy them online here: http://www.biconet.com/biocontrol/hypoaspis.html
and you will have more than enough. Get a friend to split them with you and share the cost!
Hope that helps.