The idea behind this is to have OBD monitoring integrated into the car. In this instance, the head unit is simply being used as a convenient monitor or display. You wouldn't be able to display your Raspberry Pi through a laptop unless the laptop had some sort of provision to be used as an external display, and I can't think of any that have that ability. But really, if you were going to use a laptop, you might as well use OBD software available for PCs, the Pi would be completely redundant.



You can get a head unit at pretty much any store that sells car audio products. If you can't find one that's compatible with your Saab's dash, or you don't want to buy a head unit as they can be quite expensive, you can always get a regular Raspberry Pi touchscreen and an appropriate all-in-one housing, such as the pictured ones I found on Amazon, and mount it wherever you like. I would probably go this route to keep costs down, and be less intrusive to the overall dashboard layout.

