BBQ:
In the 80's, I made a very simple lights on reminder. Only problem, the buzzer didn't last 17 years and had to be replaced once, The heat killed it.
Here me out. My solution was sound a buzzer when only the Driver's door is opened. OK, so it won;t work if you "go parking" at the park and forget to turn off the lights. It won't work if you exit from another door either.
It's super simple. Most cars switch the 12 V to the head lamps and most cars ground the door switch when the dome light is on. So now, you have an ah ha moment.
Connect a buzzer from the door switch to the headlight relay feed or head light. Well not quite.
In my vehicle, there was a diode on the driver's door for some other driver door function. I wired another diode to the switch for a "diode OR". I also put a 200 PIV diode in series with the buzzer and your done. All of the wiring I needed happened to be in the Driver's kick panel. So, you have (+12 from headlamp), a buzzer, a diode, and yet another diode in series. The other end goes to the door switch. Bingo!