I have found a company that is making a dashboard system for EVs running up to 200 volts. It uses a piece of hardware with a current sensor, thermistors, etc. that connects to an android device via bluetooth and sends the data to an app. This allows for a very elegant instrumentation solution. I am planning on adding such a system to the Mercedes. Right now, the unit works on pack voltages up to 200v, but he has a high voltage version that he is looking at developing now. You can find the device and some more information here: Power Watcher. It is also discussed in this thread on DIY Electric Cars.
Assuming he releases a higher voltage version, I will use it to drive a large, Tesla style panel in my Mercedes. It will show power details and also drive the entertainment system from a cheap Android tablet mounted in the console. It would take the place of the original radio, most likely.