I went with Carman for Nokia's Maemo platform and a generic Bluetooth scantool. The advantage of this setup is that the Nokia webpad serves as an in-car media player, GPS unit and car computer, providing me with real-time diagnostics, positioning and entertainment.

For fault diagnostics, I gave up in the end. At least for my car, (an Audi S8) it seems there are error codes that are manufacturer specific. Without a translation table, the error codes aren't particularly useful and I couldn't find any software package that included them or, indeed, just the Audi S8 code table. Happy to be proved wrong here if someone else knows better than I do..

This reminds me of a comment from Brian Behlendorf concerning the design of the Apache License to allow for modifications of the code for commercial release without accompanying source code, in contrast to the GPL. Behlendorf said that this was deliberate because the Apache Foundation believed that supporting the web protocols was more important than the keeping contributions to the Apache code open source.

Interesting to see this sentiment echoed from the client side a decade later.