I've started a flex based front end, utilizing Adobe Flex2. The first app I have created, and is mostly complete with a rough front end, is an MP3 player designed completely around a 7 inch touch screen. It allows library browsing (large button base), playing song information, visualizations, and other standard features. Again, it is easy to use on a 7 inch screen.
The second project I am working on is a front end to control a Yeasu FT-897 ham radio, that supports everything from UHF down to HF frequencies. The radio is currently mounted in the back seat, and the controls are really hard to use anyways, as they are small. This will give me the standard most used functions (and feedback information) on a format that is useable while driving.
The third project on this that I have not started, is a standard ODI interface for car information.
For serial I/O connectivity, I am using a simple Jetty based java application to allow I/O that flash/flex does not support. Flex/Flash comes with base support to do HTTP, and binary sockets as well (for async information).
The best thing about Flex is it is very easy to change the whole look and feel of the application utilizing an MXML (read XML type file). Colors, positions, control types, etc. can all be changed. I am utilizing a code behind technology that allows for changing the GUI without messing with any actualy actionscript code.
It is a definite work in progress, but I am really happy with the concept and ease of implementation. I have been using a laptop, but just purchased a car computer from this site to better withstand my off road driving. I have a 2004 Toyota Tacoma that already has ALOT of electronics in it (ham radio(s), Solar Panel, Second Battery, XM Radio, Large screen GPS for Topos (Lowrance Baja) and a few other goodies. I plan to replace the whole radio panel with the 7inch screen. The other stuff stays, though, since they all have their use (I am part of a Search and Rescue team). I want to keep the large screen GPS, but use it to drive a 'Turn Directions' based software. Nothing is available on flex, so I plan to use IGuidance.
I will try and keep people informed as my work progresses. I can answer any questions on this if people want to know what I am doing.