The battery tester I have will put a load on the battery and calculate its life. It’s a bit different than a normal meter. I find it useful to know if my battery is good before I take a trip or once in a while, as it’s better to know more than just knowing the voltage of the battery. I don’t think it’s really necessary, but I find it useful and didn’t cost me too much.

A normal multimeter is great for thousands of things, even the cheapest harbor freight one is a great start. (you might find a coupon for it for free).

I thought BMW wanted a subscription for heated seats. You know, the seats already in your car but software locked with a paywall.

Electrical meter

Tire air gauge

Tire patch kit

Air pump

Brake reset tool (forget exact name, I paid $10 and it pushes the brake piston back in when installing new brake pads)

Tire thread measuring tool (know when you need new tires)

Battery tester (test how many cca remain)

Battery acid tester

Radiator coolant tester

Distilled water to put in battery

Coat hangers (metal hanger can be cut and bent to hold things such as the brake caliper)

The tire patch kit saved me a few weeks ago.