There's an idea kicking around in the egghead community about a notion called V2G, or vehicle to grid, where parked hybrid or electric cars would be plugged into the city grid and used as a distributed power storage medium. Car owners would collect a fee as the cars would be used as a buffer to store power generated in off hours for use during peak times. The concept would do away with the need for backup generators and further offset the higher costs of hybrids. What the idea won't do is work without ginormous cross industrial and governmental standardization the likes of which will never be seen in the United States. To Europe, eggheads! [LiveScience]
To make that work, all you need is a modern electronic meter... like the ones already being installed throughout the Toronto area. You can already sign up to save money by having Toronto Hydro dial back the consumption of your AC at peak load times. I'm sure having a hybrid as a utility battery bank is doable right now provided that the charger/electronics in the given hybrid allows for it.