Idiot light modification ?

I completely agree. Back when I was a kid I unhooked the idiot light from my 70 Chevelle and put a gauge under the dash. One Saturday night we we're cruising and some time it lost oil pressure. With the gauge out of eye's range I never noticed it until the engine was knocking hard. Learned my lesson then to keep the idiot light working and add a gauge if I wanted to know the oil pressure.

I've thought about the buzzer idea TB mentioned. Sounds like another good idea

I have taken a few liberty's with the electrical and lighting in my car.
For example, when I swapped my overhead interior light to LED's I rewired the door switches through the map light switch instead of the headlight (twist switch) and added a small rocker switch to the back of the overhead fixture. (facing the back seat)
It gives the passengers control over the overhead light if they want it, but I have the final say so with the map light switch.
Also, you can turn off the rocker switch on the back of the overhead light so the interior lights don't come on at all when you open the doors. (if I ever have a use for that) :D

If I ever sell this car I'm going to have to write up a secondary uses manual for how things work and what they do.
Like the line lock circuit, since I have a line lock as well as brake lights when the lock is active, but without a switch in the front line to activate them. (my own little design)
The line lock electrical also powers the brake lights, but a diode in that wire keeps it from activating the line lock when the brake light switch activates.
Simple as hell, and works perfectly.

This is the image I use for advertising that product.
Now if I could just get all the line lock sellers to include this with their locks I'd be golden. :D