How about an old netbook ($100 on EBay or less) that’s set up to e-mail you every half hour? Remove the battery. If e-mails stop coming to your mobile, you’ll know it’s time to call your neighbor to check what’s going on. There are also automatic dialers that dial a phone # if power is lost, but they will only work if your phones aren’t dependent on power (i.e. not cable or VoIP).
Any battery/UPS system under say $500 won’t run an A/C for long. A/C’s draw 10 amps minimum, so 1200W or 100A from a 12V battery. Meaning that assuming a 100% efficient system, a car battery will only run it for about half an hour. Not to mention that the transformer has to be correctly rated, and output waveform needs to be correct to power a motor as opposed to a switching power supply in a server!
Self-starting generators are also expensive and need to be mounted outside, unless you want to gas your dogs.
