Hi, the SCK has an additional usage possibility (quite obvious by the way) I have just explored:
My house’s power supply sometimes goes off due to the differential switch triggering without any apparent reason (I have heard this happening to quite many other people, too). If this happens when you travel this can mean that e.g. all your refrigerated food ends up rotten. Although leaving the keys with somebody, you don’t want to bother them getting there every day.
The trick is to remove the battery from the SCK and use it with its power supply only, so you can monitor from anywhere in the world if the house power is still on (the SCK continues sending data).
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You can also use a rearmable differential 
Ups, didn’t know that exists (getting slightly older)
So the idea is not as good as I thought, but anyway…
Thank you!
Your idea ir far cheaper though. 
Yes, just a beer for the key tenant 