Mark,

Re: "Simple, eh?"

I'm familiar with the everything-is-a-file philosophy of Unix and how to use it. Nonetheless, for the purposes being discussed, I stand by my suggestion that using a small filesystem is the most flexible solution, as well as being among the easiest.

A generic "small pieces of persistent data" filesystem which is mounted rw in the car would provide all applications with space, and a namespace to avoid collisions. The time to fsck e.g. a 1 meg partition is trivial... and if the file open mode is O_SYNC then the chances of data being lost due to corrupted metadata are pretty slim.