Bidirectional Charging During Grid Outages

David asked a great question on my solar battery system post: why buy a small battery just for emergencies when electric cars have a large battery you can also use for other things? [1] This would be great, and seems like the obvious way for it to work: when the grid goes down the panels can charge the car when it's sunny, and the car can power the house when it's not. Unfortunately as far as I can tell the only way I could do this today is with a Cybertruck, and other systems are a long way off...