Oh if you want ideas, I've got tones of those!

A recipe database that has different ratings for different people do it can suggest a meal everyone can have and everyone will like and also uses up ingredients that need to be used up before they go bad.

A thermostat that looks its calendar to see what events it was invited to, sees who else will be there and what temperature range they prefer. Then it chooses the most energy efficient acceptable room temp, and starts heating or cooling far enough in advance that it can use the minimal energy to accomplish this (e.g. stage 1 heating, blowing air from a warmer room to the one that needs heated, etc.).

Or an automatic crop watering system that is purely mechanical and ensures that the garden is always watered and doesn't rely on motors, pumps or electricity.

Or... well you get the idea 😂🤓