Gary - Don't sweat the accuarcy part. Digital or analog will typically get you +/- 3 to 5 Deg 5. No better. Reality is if that uncertaintiy is the difference in making a temp decision or not, you are already there...

External vs. Internal is an interesting question. Personally, I like the patient being able to tell me how it is feeling... In my experience, the transducer itself is the flakiest part of the gage "system." It's highly unlikely that a bad gage gives good readings, so if you see an odd reading on the truck's computer bus, then you can quickly locate a point of interest, validate the reading and add additonal intrumentation as required... The more bus data you can get, the better. Think AutoEnginuity...

Just my $.02.

Cheers