Auto top up w/ rain sensor?
There was a Cadillac in the 50's which had this feature and it was a big selling point. I'm sure it's possible because I have seen people convenience close their tops.
2003 BMW 325xiT "Audrey"
1987 BMW 325i "Lydia"
1990 Audi 90 Quattro Sport 20v "Chloe"