TL;DR: Is there a cheap and simple tool for detection of very brief mains power outages?
Long story and explanation:
Yesterday and today we experienced three or four interruptions in mains electricity supply - some appliances with switched power supply units (PC screens, LED lights) flickered or failes for a very brief period of time, while appliances with good ol' transformer+rectifier setup (like the clock display on the oven panel) didn't seem to be bothered by them.
I firmly believe that we have had many of these in past two years, as these glitches manifest themselves by various strange effects that I can't find better explanations for (fridge-freezer box somehow stops refrigerating and sounds an alarm few hours later, the wifi access point seems to brown out and functions very erratically until next restart, one PC headless restarts itself).
I've had the utility guy over today, he measured our mains tap (voltage, impedance, inter-phase impedance difference etc.) and he said everything looked good on their part so he can't really do anything. He further said I need to check my own wiring, which I will do, but I suspect there is something amiss at the utility since the whole building of 5 units experinces similar weird occurrences as we do. Lastly, he said I should talk to our neighbors and ask if they have similar problems. If they do, he'll come back and do more checks (we are connected to an underground cable which may be failing somewhere but he has no means of detecting that before a full blown failure and as per his measurements right now everything looks good).
Now it took me some two years to actually witness this phenomena, as it usually happened when I was away or in broad daylight with no lights on, and one could only guess we had this brief outage hours later when the fridge/wifi problems manifested themselves. I'm a bit on the technical side of thing, whereas my neighbors are not. Which means even if I ask them, I doubt they won't be able to give me a definite answer whether they, too, get these glitches.
So I'm thinking if I could get them some simple and power efficient gadget for them to plug in to their own socket somewhere, I could just ask them whether the thing has gone dark/silent/pop/kaboom lately, and we all would get a nice answer to a complicated question.
All I could think of was a relay feedback loop which must be manually "activated" and the loop will open on power failure in the relay. But I would prefer a off-the-shelf solution one can buy chaply in a shop, as I don't really want to give my nice neighbors a strange gadget I engineered to put into their wall sockets (and I'm not certified to manufacture such things either).
I specifically don't ask about checking my own electrical installation, as I'll have a professional do it. Also our wiring is three years old and had to be checked officially before we were actually allowed to move in and use it.
Our location is the Czech Republic, Europe. We have three phase 240 V burried cable mains with 8 separate meters for various units, staircase etc.