There is a "keep car cool for pets" mode that also works for children. Has a helpful message on the screen so passing do-gooders don't have to worry.

An automated system to prevent harm caused through parental negligence would be interesting, but how would you even detect that a baby was present? Maybe some kind of 'have' token attached to the carrier or car seat? OTOH that could cause more harm via accidental strandings. Would be interesting to search for an elegant solution.