@ritchierich has it right; while the Internet is great for remote (away from home) monitoring, one doesn’t want to depend on it for basic safety and ‘important’ actions if reasonably possible. That is the fundamental problem with using IFTTT – it is solely driven from the Internet.
Having “home network” on mini-UPS devices allows Apple’s HomeKit to be a bit more “available”, albeit that their automation rules are quite simplistic. That at least handles short-duration power outages.
Now, from Sense’s perspective, if smart plug “device detection” were able to stay reliable when the device was no longer on the smart plug (i.e.: it would learn to recognize the device from the pattern while no longer needing the assist of the smart plug or the “Flexible Sensor” - aka Dedicated Circuit), that would be quite helpful. One could leave a device on a smart plug for a while, Sense could provide some kind of ‘tag’ in the app showing “I got this now”, then that smart plug could be moved to a different, perhaps previously undetected, device.
That seems to be especially do-able for devices which don’t have an Always On component (like pumps, electric heaters, …). Smart plugs would probably need to stay in place for variable-usage devices with an Always On component, though.
This could be a viable, reasonably automated, and perhaps reliable, method of ‘training’ the Sense device – something high on everyone’s “wish list”.
Sidebar: (need to find the right topic for this): It’d be nice to have some means to “buffer” the Sense device itself (and its data collection) through short-term power outages. My home network stays up and connected to the Internet through perhaps a few 10’s of minutes of a power outage; might need a new Sense hardware revision to provide for that, though (e.g. a DC power port to connect to battery or similar short-term supply). Two Sense versions: v1 = Simple home monitoring; v2 = High-availability monitoring. I’d do that upgrade!