They have been around for a long time now... I think they appeal to people who buy honda's and look for ways, and ways, to improve performance. Some people can NOT own a car withought doing modifications. Honda owners are famous for this. Blue bulbs, a.k.a. fake xenons, K&N air filters, that tornado thingie... I don't believe any of them really make a difference, but they do seem to make owners feel a little better about their cars. Perhaps it's because they think their civic, cr-v, accord, md-x, or whatever, is just a little better than the millions of other civics, cr-vs, accords, md-xs or whatevers.
Don't waste your money on crap like this. Either trade up for a car that has more power (if you really feel you need that) or get accessories that matter... Like rubber floor mats, splash guards, or side mouldings... Things that protect the car vs. violate the warranty.
Back when I had a CR-V, I looked at all kinds of crap like this too, but eventually realized that it was all stupid. I have not received my md-x yet, but like my audi a4 quattro and mercedes ml-430, I plan on adding no features at all... I picked this vehicle because it already has everything.
BUT... If I was to add or change out an under the hood option... I would do what I did to my CR-V, which was pull out the vw beetle horns and replace them with a pair of tuned air horns. Stupid? Maybe... I thought they were kinda funny. Believe me... When I honked, people got out of my way!