I was hoping to mention it later (depending on how the conversation went) but since he's already brought up the subject, I have to agree with my friend @Stan Galat- an oil pressure gauge would be much more useful (for all the reasons he mentioned). A remote sensor for air temperature mounted temporarily in the engine compartment would be a useful thing to have for experimental purposes- the closer the inside temp is to outside ambient the better the engine will run, staying within it's normal operating parameters/being closer to optimal tune more of the time and (if you believe some of the old guard in the VW performance world) it will last substantially longer too.