I've noticed several threads regarding the "electronic superchargers" that seem so prevalent on E-Bay. Obviously the general opinion is "junk" and I have to agree. But, there's nothing wrong with the principle (which is why I think these things keep popping up). So, being bored, I decided to investigate a bit. Here's some info I found.
This site has a pretty comprehensive explanation of what they are, how they work, and why they don't do what they say. Instead of plagarizing this guy's work - I'll just list the link
http://www.dansdata.com/danletters105.htm The article is the 4th headline down. What's interesting is that most of these are apparently bilge ventilating fans for boats!
I did look up the data on Thomas Knight's ESC Electric Supercharger and was pretty impressed. This is a real supercharger driven off of battery power (requires 1- 3 extra batteries). I found an interesting article in Turbo Magazine about the product.
http://www.turbomagazine.com/tech/0406tur_knight/. You can also check out their website at
http://www.boosthead.com/home.php From what I can see, this is apparently one of the few, if only, legitimate electric superchargers out there. But as such, it also cost nearly $1700.
I don't know how well it would work with a Boxster but the bonus seems to be that it's about as close to a Mad Max switchable supercharger as any of us will get! Anyway, check out the links, there's some interesting information there.