I've looked into building my own before, and the ones you see on eBay, as well as at
www.electricsupercharger.com, are of the same design... It's just a powerful electric hobby motor inside a R/C jet's ducted fan unit. You can build your own for around $70 or less, iirc.
electricsupercharger.com claims to produce like 1 psi of boost, but that really depends on how much air the engine is drawing. The smaller the displacement and the lower the rpm, the less air required and the more boost it's going to be able to provide. So, it *may* be able to help out the low end power on an Integra, Civic, etc, but I'd still want to see it before I believe it.
It also supposedly draws about 50 amps. A 3rd gen Integra's alternator can only supply 90 amps max for the whole car, so 50 is a *huge* draw on it. So, it produces little boost and draws a lot of power; not very efficient.
That's not to say that the idea of an electric supercharger is bad, but you'd likely have to use something that produces more CFM and draws less power.