I’m not sure that I completely understand what you are looking for, but here’s a few suggestions if I DO understand. First of all, is your hub located where you can also plug that into your UPS? That would help get around some issues. There are several options for power on/off notifications. If you are handy at building electrical projects check out this link Power Loss Alerts It’s basically a powered relay that’s plugged into a wall socket and connected to a dry contact sensor such as Ecolink door sensor. You can set it up in the app to notify you with wording of your choosing when the sensor opens or closes (The info on the link refers to 240 volt power, but use a relay suitable to your voltage needs) There is also this https://www.amazon.com/Enclosed-AC-Protection-Bounce-Terminals/dp/B017743I7S/ref=sr_1_2?keywords=outlet+relay&qid=1570981641&sr=8-2 from Amazon that you can connect to a dry contact sensor with the same end result. Of course this only works if your hub is powered .
As far as temperature notification, there are many Zwave sensors that can report temperature, both battery or mains powered. MultiSensors usually send temperature info and a lot of door open/close sensors do also. I use an Aeon Multisensor 6 in my pump house to notify me via the app if the temperature drops below 32 degrees. Again, however, your hub must have power, hence the UPS. Hope this helps.