Picking up dashboard signal

Hi. 

Has anyone ever tried picking up a copy of the (digital?) signal going right into the dashboard? 

I am asking because, ideally, I would like to "real-time copy" all those numbers and log them down to an SD card, an probably adding some GPS signal using a raspberry? 

The unit would be housed near the dashboard (a lot of space there) and powered by either the dashboard cable (it should have a 12v constant power supply) or by the external power supply (cigarette lighter), on available in runni g engine. 

Anyone knows if that is possible? 

What drawbacks should I consider? Would i somehow interfere with the original, untouched signal? 

Thank you

Marco