Many modern ones have a door open sensor that allows for the dishwasher to display that dishes are clean after a cycle until the door is opened and fully closed again.

That doesn't help, however, if users are lazy and don't unload the dishwasher after opening it to grab a clean plate or whatever.

It's a nice feature that can be added with existing sensors and one line of logic in the uC. Another one I noticed recently is garage door openers with the photo transmitter/receiver ('beam') to stop the door if someone blocks it can use that same beam to turn on the light if broken when the door is up. Handy if entering a dark garage from outside.