Ok, so I looked at that readme and the app is a bit different than I thought. Apparently, it relies on the Zen15 driver (DTH on SmartThings) to pretend it's an acceleration sensor and report anything above a specified wattage threshold as "active," then the app tracks if that happens too many times in the specified interval and notifies you.
I don't think there's a native driver that does that for a switch/outlet on Hubitat, though it certainly would be possible to write, modify, or port one that does. However, it seems to me that it would be better to simply rewrite the app to use power reporting from the device (or any one that supports it) unless there's some advantage to doing it with the driver that I don't see. It might be possible to rig something up in Rule Machine that does something similar, but I'm not sure how easy that would be. If I have time, I'll see if I can rewrite the ST app, but no guarantees. 
In the meantime, it looks like that ST app would work verbatim, as long as you have a driver or can port a DTH from ST (should be easy but if you find one, but I'm sure lots of us would offer to help) that works how the app expects.
