I suppose a beep that sounds very different would get their attention, like for pilots in plane cockpits. A terrible stand-up comedian suggestion would be to reuse the plane's "retard, retard!" for parents who forget their kids...

It's not about annoyance, it's about whether it's effective at all.

If the car dings every time you turn it off to remind you "check back seat", it doesn't matter if the alert is completely unique and obnoxious and annoying, you will be trained to ignore it and it will quickly become ineffective.

There's a whole field of study here ("alarm fatigue" or "alert fatigue") that's generally looked at in terms of things like healthcare or aerospace. For example, there's a study in healthcare[0] where they found that when dealing with a system warning about drug interactions (including critical dosing errors, fatal interactions, etc) providers overrode 96% of alerts. Their "high priority drug-drug interaction" alerts were overridden 87% of the time, and on review only 0.5% of those were deemed appropriate. Other studies[1] have directly attributed this to repeated exposure desensitizing people and training them to ignore the alerts. People have died because of this.

I have a kid. I can't imagine the horror of being in that situation. I am certain that it would completely and utterly break me. I am fully onboard with a system that prevents this happening. I would be fully supportive of regulating a system that prevents this from happening. More unspecific beeps and dings is not that system.

[0] https://psnet.ahrq.gov/issue/high-priority-drug-drug-interac... [1] https://psnet.ahrq.gov/issue/evaluating-alert-fatigue-over-t...