Hmm, I've not heard of them? I would think most airbrushes are portable provided you have an outlet for your compressor.
Oh I see, they come with a small compressor canister type thingy. Well, the only thing I would be wary of is the PSI. It it's too low you don't get a nice spray. It was recommended that for airbrushing ponies PSI should be around 30. These portable ones (the ones I looked at anyway) seem to top out in the teens. The airbrushes are also single action, which I have no experience with.
Honestly for the price? I would invest in a good double action brush and a small compressor. My Paache VL, which is a very nice airbrush, was 76 and I think I paid about 45 for the compressor. It's a small one, I'd call it portable. It was for make-up application but the PSI goes all the way to 100.
If you can find one of these portables on sale and you want to try it out, go for it, but I wouldn't spend over $50 for one. Just my thoughts