I know this is beating the dead horse, but this piezo thing, aka accelerometer, keeps bugging me. There are several companies who have a range of standard products for monitoring vibration of electric motor bearings. It looks like a cousin to the knock sensor. These things are small, mount via stud or adhesive, and will live at engine temp. The signals rout via cable to a little box which is monitored for waveforms, etc. Sorry, that's the extent of my mojo, So so tap an electronic engineer- Boxter owner next time you see him and ask.
