I've mentioned it elsewhere, and this is super niche use, but if you have two cats (or dogs I suppose) that you free feed different foods, these gizmos are great. They read the cats' chips (or a tag on their collar) so that only the appropriate cat can get to food.
They're not cheap ($150), but they're great if you have a need.
https://www.amazon.com/SureFlap-MPF0...dp/B00O0UIPTY/