Travel pillow
I don’t know if you use your car for driving to work and back home, or going camping, or.. if you are a driver, like long distance driving. If you are, you must know about travel pillows.
I see a dozen of manufacturers, all bragging about how warm and fuzzy and neck tension releasing their pillows are. And i believe them. Occasionally i drive for 3, 4 hours and my neck hurts, and my ass also 
Most new cars have already implemented this kind of car gadget, hours and hours of testing really paid off in some cases.
Bon voyage !