+1 on the UPS. alot of hardware(or even automotive) stores sell DC
inverters. some come with a decent sized battery and inverter all in one, or you can buy the inverter itself and then attach it to a battery. the nice thing with DC
inverters are that once they drain the battery, you can charge them again from your vehicle, granted its not an instant charge and youll have to run the car while charging, but atleast youll have a semi-sustainable power source.
also the downside to a UPS, (atleast in my eyes) is that once they are drained, they can only be charged by plugging them into an outlet, of course, unless you had a dc
inverter to charge them from a vehicle
so in theory, if you had a UPS, the power goes out, your UPS kicks in, once it dies, youll have to go to someones house (that has power) and charge it again......