As a former electrical engineer, I have some ideas on electronic devices that could be added to EVs to make them more useful. A description is given of each idea below, and a link to more information on the idea.
This design uses a "D" type flip-flop to latch the main contactor on when the pot box switch is activated, and off when the brake pedal is pressed. It's fairly simple, with a couple of design additions to make it more fail safe for use in a car.
This design allows monitoring of each individual battery. It's user interface consists of a numeric display and a 8 segment bar graph. Each battery is assigned a number, when that battery is displayed on the bargraph, the number associated with it is displayed on the numeric display. The bar graph has 8 segments displays state of charge in 10% increments, from 100% to 20%. The default mode is round robin monitoring of the batteries, displaying each one for 1 second.
There are three buttons on the unit. The first is an on/off button. The second toggles the unit from round robin monitoring, to continuously monitoring only one battery. The third button functions only when the second button is active. It allows you to single step through each battery.