Universal budget swivel seat base for driver or passenger seat. Could require some modification during installation (it could not have holes for your particular seat model)
Very configurable car scanner/meter with a lot of data including fuel consumption, oil temperature, distance and time of ride, engine load and many more. Very useful to old vans without smart modern displays and computers
Simple and cheap tire pressure monitor with digital display with pressure and temperature monitoring for each tire. Easy to install instead of standard plastic cups. Works from solar power or MicroUSB cable. Turns off and on automatically
Breaking light with a parking camera. You could choose the option with a camera only or add a display to place as a rear view mirror. A good way to install 2 in 1 device for safety parking
Portable car jump starter (booster) for starting your engine with a dead battery. Also has 2usb ports, 12v output, and laptop charge adapters. So its also a very capable power bank and camping device
Buying your vehicle with useful tools. Dont believe car seller, check paint thickness yourself and get information on what parts were damaged and repaired. Costs few bucks could save few hundreds