Low Voltage Battery Disconnect, Headlights, Domelight

Anyone know of a low voltage power disconnect add on ? My wife has a tendency to leave either the headlights or dome lights on in her van. surprisingly enough her van a 2012 kia Sedona doesn't have one factory. One issue I see is keeping memory if it does disconnect. I was thinking maybe 2 different circuits one for the headlights and on for the dome lights. That way I don't have to worry about memory. I was also thinking of just using relays to interrupt the ground on the headlight and dome light switches. so the key would have to be on to use the switches.If i Can't Install it    I Don't need it   Joe

I've used Priority Start before (it kills power to the vehicle when it drops to 11.7 volts IIRC). I ended up removing it later anyway. You connect your positive battery cable to it and then connect the attached cable to positive. In my case, this extra connection would work it's way loose later eventually (the post adapter simply unscrewed which could potentially leave your wife stranded as well). There's a small ground wire with a quick disconnect you remove/replace to reconnect the battery. You could always extend this and put a toggle switch somewhere inside so you could reset it from the driver's seat. On one of my cars, I actually have a backup battery installed at the back (still haven't done the other car since purchasing a couple months ago). There's either a 150 or 200 amp breaker at both ends (can't remember), and a contactor in the back, with 1/0 gauge running in between. It's only connected to the starting battery when the car is running, unless I press a button under the dash (essentially giving myself a jump start). I also carry one of those lithium ion booster packs (make sure to turn off for storage) in each car as well as quality jumper cables. If you have a wiring diagram or can figure it out with a meter, I would probably install a buzzer as a reminder. Alternatively, install relays as you have suggested so the key needs to be on for the headlights/dome light to receive power.My ex once told me I have a perfect face for radio.