I guess I can answer my own question on this one. I have a Smoore 401 PT now, and I've had a chance to take it for a spin. I put in on a 700 mA wall wart, and had two things tell me that 700 is not enough. First, there is very little vapor. Second, it only works half the time (it flashes the other half of the time). Since you can only be sure that your PC can put out 500 mA, it's not a good idea to use it from your computer.
So: this PT is passive, no battery. Don't use it unless you have a 1000, or better yet, 2000 mA wall wart.
