Keeps the windshield frost free all night long; get in the car, start it, fold the cover, go.
If it's that easy, I'd consider one (and where would I get it?) - but I have doubts:
1) I'd still have to scrape the side/rear windows (failing to do so would be silly, Sir).
2) Does the cover repel water/ice formation, such that a brief shake would remove all snow, etc from it? If not, then you'd be putting a snow/ice-covered sheet in your trunk...and then you'd have a bad time.
3) How much does this magical device cost?
4) How long does it last?
5) How do I find time in my day to be on this forum so much?