Second House Remote monitor

My issue with IoT has always been connectivity. Remote premises always lack this...We have a vacation house by the beach and we don't have DSL in it, neither I fancy paying a monthly fee to keep a GSM card working just for this.

GSM and Wifi are wide bandwidth networks that provide a lot of traffic capabilities and, in turn cost "some money" to keep up. Do I need to send several Mb a minute for this? No, I just need some bytes every several minutes, but network operators don't have a "reduced network" with "reduced price" for just this purpose.

Then...magically, SigFox showed up in my life. Not sure how, I stumbled upon this technology some days ago. I needed to further investigate it...

Surprisingly it was everything I was looking for. You send short messages (up to 12 bytes of payload), no more than 140 times a day (every 10.2 minutes), it "bridges" to your favorite IoT cloud (mine is ThingSpeak) and I checked the coverage map and my country is almost 100% covered!!

Well, this is the time now to start monitoring my vacation house.

What would I monitor?

-Temperature and humidity. Why? Why not! It's what everyone in IoT starts monitoring, as it's cheap with a simple DHT22 module, and it let's me detect: Extreme (and abrupt) temperature change: Broken Window? High temperature? Fire. Sudden Humidity rise? Water leak. Good enough so far

-Power outage: I have a sump pump and a fridge that are quite often left working in the house. If I have left food in the fridge (if we are going back in a few weeks) and the power goes out due to a sudden power transient, my food (and the fridge!!) will be lost, stinking, to say the least. Also during heavy rainfall season, I can't leave my sump pump off!! I would like to get a warning for this

-PIR and Smoke detectors: I don't have a real alarm at this house. I would like to get a warning if I get someone in my house, quite often it would be myself who forgot to turn the warnings off the first time I go to this house, but I need to know. Also a smoke sensor will be useful as I leave the power on, and there's always the risk for a shortcircuit/smoke in electric devices and appliances.

The usual monitoring sensors would be sending updates every 15 minutes (to keep up with the SigFox limits) but the "instant" sensors (power, smoke and PIR) would notify right away, as they would be considered "priority alert".

This device could be powered off a pair of AA batteries which would last 6 months, as I visit this house more than 2 a year, but it could still be charging the batteries with either regular power or a small solar panel (when placed closed to a window)