For serious cold and a great solution, try http://www.hotronic.com . I havent had to ultra test them yet, but so far so good.

The thing to do would be wire up those heated foot beds to a bike light generator as a back up power source.
My secrets for winter rides are wool socks, neoprene booties, and the knowledge that no one ever died of cold toes. Once they go numb I just quit worrying about it and start thinking about my hot tub.

I've never tried this on a bike, but I use those toe warmers that stick to your socks when I ski and they work like a charm. You can get them anywhere, but I usually stock up at REI.

Rollers.



Seriously, the booties work best for me.

polypro socks..thin or medium weight..then get a sheet of kitchen shrink wrap (cellophane..etc..the real thin clingy stuff) and loosely wrap it around your forefoot..not super tight..just providing a wind barrier. Then put on your shoe and use the neoprene toe warmers like QR and De Soto make. Then booties on over the toe warmers. I've ridden in really cold wet weather and my toes are never a problem doing this..something else always gets cold first. Good lluck