Re. automotive, I've also heard there is/was an overlapping group of Palm + auto enthusiasts. Quite possibly they're using something like OBD Gauge: http://www.weidefamily.net/vanagon/Pending_Content/Engine_Co...

Getting that working up is on my to-do list. Today I use some Python scripts to read engine codes and such, but it's not like I always have my phone or laptop on me. :)