Even though I've never tried any of the devices you mentioned, I'm going to give you my opinion. But if you're seriously thinking of getting these devices, it would be a good idea to check out some testimonials from people who use them. Don't rely, though, on testimonials posted on the websites that sell the devices.
Face master and Dermawand are radio frequency treatments. The devices produce slight contractions of the facial muscles. I don't think these delicate contractions are of sufficient force to tone up the muscles. However it's probably better than nothing.
Light Stem is a light therapy device that supposedly stimulates the skin's natural collagen production. My only suggestion here is to study the biology of collagen production and decide for yourself if this pricey bit of equipment is effective. Read the excellent articles about collagen and other topics by Dr. Todorov on SmartSkinCare
. His informative articles on skin care are the real thing - honest and intelligent. Take a look at Dr. Todorov's forums too.