First of all DDuB420 - that's the coolest setup ever.
And for the people that ask why, the answer is simple -- because you CAN!
I've got an Intel NUC that I use for my HTPC Plex server and I want to get another to do what you are doing. Can I ask a couple questions?
1. Do you have to have a bypass installed to use your PC while driving?
2. Can you post a wiring diagram, of how you have everything connected?
3. Are you able to connect to your iPhone as a hotspot to get in-car 4G?
I definitely want to do this.