Tim you are thinking of a pressure wave supercharger otherwise know as a wave rotor. A copyrighted name for one is Comprex. They have the response of a supercharger but don't consume engine power like superchargers do. Wave rotors also weight less then both turbos and superchargers, and don't require exotic alloys like a turbo. Both NASA and MSU are doing research on them right now. They have many uses outside of a turbo/supercharger replacement.
http://www.egr.msu.edu/mueller/projects_waverotor.htm
http://www.grc.nasa.gov/WWW/cdtb/projects/waverotor/ I know Ferrari tried them once but have not heard of any other team trying them.