Something to consider is a battery backup for valve and ignition control circuits. Typical 24 volt DC control voltage doesn't take hardly any current. Thus, a small battery supply would be sufficient. Likewise with electrical ignition sources. Of course, forced air (fans) furnace or inserts require significantly more power, so battery backup for those systems may be impractical.

As someone else alluded to, a couple good dogs to snuggle with can be pretty handy, provided you can get them to lay still long enough. The colder it gets, the more willing they are to huddle up.