gotcha, that’s a tough one. Again… the only thing I could possibly point to are the Nokia internet tablets. Because they are Open Source you might be able to modify the RTOS you have to run on them as the native OS (I believe) is able to do what you describe:
Here is the tablet: Nokia 770 Internet Tablet - Wikipedia
Here (might) be an example of the OS being able to provide Real Time data:
http://openbossa.indt.org/carman/
All the internet tablets (770, n800, n810) are basically the same so you should be able to do this on the newer hardware as well.