Oh … I guess I am misunderstanding. Are you looking for an OS that supports this so you can write code to use the feature, or are you looking for a piece of hardware that already has code written so you can see the code in use on an existing mobile product?
Do you already have the hardware piece that you know can provide real time data, or do you need that as well?
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: