I have been exploring the microphone front lately. I have found some good canidates in lapel/tie pin microphones used for presentations and stuff. The problem with these is they tend to require a battery and I don't want to have to switch a mic on and off.
My car has a built-in mic grille where the OEM cellphone kit goes, so I need something sort of flat to mount behind that. I was probably going to just end up tearing apart one of those standard beige boom mics that comes with every soundcard on the planet and hot-glue the element onto the back side of the grille. I suspect that it will function quite adequately for what I need!
At least it will be cheap.. I have tons of those mics. If it doesn't work, at least I didn't ruin a $35 mic