Power outage and low temp notification project: advice needed

Hi, I am a ST newbie.
I am transitioning from Iris at my weekend home. I have the Gen 2 Hub and using the new app on my phone. I managed to connect my Iris Radio Thermostat CT-100 last night which is the only device I really need. I don’t have a C-wire, the boiler is a simple two-wire system so the battery powered CT-100 worked well for me.
With winter coming I need a reliable system to (a) notify me if / when a power outage occurs and comes back on and (b) notify me if the temperature drops below a preset level in the house or in the basement. I had my Iris set up with the wifi router on a UPS and the Iris hub on direct mains power. If I lost mains power, the router could keep going for awhile and the battery powered Iris would notify me of the loss of power. Of course, it also let me turn up the heat before my arrival at the weekend.
I am looking for advice on how to set up my SM system with the same functionality. I keep the setting pretty low when the house is unoccupied, so a reliable low temp notification is vital to prevent major freeze damage. I am open to getting new devices or even replacing the whole system or switching to a stand alone system if necessary as long as it is DIY with no monitoring fees, but the lack of a C-Wire limits my choice of thermostat since trying to add a c-wire or transformer/power supply would involve opening walls, redecorating etc.
I also have Alexa and a couple of Blink cameras if that is relevant or helpful. When Iris died, I set up one of the cameras on a clock in front of a thermometer and a clock which allowed me a back up temp monitoring. Hopefully there is a less crude option out there, but I am not very savvy when it comes to these systems.
Thank for your suggestions.

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.

Thanks Mike.
Yes, I can plug the hub into the UPS. On my Iris system the hub sent me a notification that it was switching to battery power which I interpreted as a mains power outage. The SH will switch to battery power too, but I don’t see how to make it send me a text or email when that happens. Unfortunately, after checking the links you sent me, I think those suggestions are beyond my electronics skills. I am hoping for something a bit more off-the-shelf.

The Aeon Multisensor 6 sounds like a good idea. I might be able to set it up with a mains light to notify me when the power goes out in addition to a temperature drop. I’ll check it out.

Thanks again.