The Penn-Plax Silent Air B11 battery powered air pump is the best I've found for emergency backup. I have 2 with several extra D batteries in case of an emergency. You can set them so that if the power goes out they automatically turn on to aerate the tank.
I have a Penn-Plax Airpod with battery backup. It plugs into a standard wall outlet and has 4 D batteries that kick on in the event of a power outage. It is loud and not worth the $50 I spent on it, but I do use it for moving fish or emergencies. On my main tank I have since took a computer UPS that I had and use it with a TetraTec deep Water Pump which has been a great combo.