turboxs have them..
www.turboxs.com.au - if you need any info send me a message, my mate works for them..
http://www.turboxs.com.au/more_info.php?ID=212
Haven't tried it but I believe they double as a shift light as well from the review in autosalon.. you have to calibrate it so that it can differentiate from normal engine noise, however I believe that's just a matter of it learning your RPM range noise..