Water injection is used to cool intake charges... But this is weird because you don't usually do it to a stock motor. Methanol injection is more common but usually you do a 50/50 mix. I don't pretend to be a pro on the matter, just from what I have seen on a friends car.
Cools intake and exhaust temps and I believe they do clean the engine decently like the site claims.
This is the brand I am familiar with
http://www.coolingmist.com/