Just spotted this project on Twitter.....
https://www.kickstarter.com/projects/resumer3d/resumer-3d-resume-your-interrupted-3d-prints-autom/description
(https://ksr-ugc.imgix.net/assets/021/276/632/f13f693a1a01cf057e2f0237f49696f8_original.jpg?w=680&fit=max&v=1526656658&auto=format&q=92&s=ac7c3cf07279f7ef4ce149962ed88c61)
It's allegedly a plug and play module for your printer that acts as a failsafe for power outages and also allows you to resume interrupted prints.
The most interesting thing is that it's less than $30 which makes it probably worth a punt.