Wood heating - Problems with power failures. Need some advice
You can find all types of power failure alarms online, with a simple search. One such device from Reliance Controls, is the PowerOUT!™




  The PowerOUT!™ is a power failure light, power failure alarm and a
  portable 6-hour LED flashlight. When plugged into a standard 15A, 120V
  outlet, the PowerOUT!™ will sound an audible alarm and illuminate three
  super-bright LEDs when your home's electricity fails. It can be
  unplugged and, using the three-way slide switch, the alarm can be
  silenced and the PowerOUT!™ can be used as a handheld flashlight that
  will provide up to six hours of cumulative light. The PowerOUT!™ is CSA
  Certified for the US and Canada and powered by a permanently installed
  NiMH rechargeable battery.


I have never used this product, and do not recommend or endorse the use of this product. This is simply an example of one such device that exists on the market today.

If you're simply looking for a way to be alerted if the power goes out, a device like this might be a simple cheap solution.