tsac I am not new to technology as I have been watching it starting from Pentium 75 Mhz, 8Mb ram, and 400Mb hdd drive, back in the day when it was a good machine, through floppy, cassette, cd, dvd, Blue Ray to internet and development of adds, cookies, streaming*.
With adds came invasive technology aka "smart"phones. When we use it we agree to be sold in any possible and available way.
Look at your Router and how many is in your neighbourhood, now think about this https://www.youtube.com/watch?v=wvaAKxL-vwE
Wi-Fi can map your location in its proximity to around your finger movement in the air, when writing invisible letters ;]
Your ISP knows that, and we all agree on that when we accept to use their service, to which we are limited today @ free* internet.
Now going backwards in history or going through US patent office you can find quiet a few which are describing how to use household lightbulbs to map location of the light, so spying was done in the past too, but today it is more invasive thanks to Wi-Fi and other technologies (Google have global signal... mhm), people allways carry their "smart"phone with them which is in itself wi-fi transmitter.
After a few delete,wait,observe,repeat cycles I have found the app causing it. It was not really an app but free* widget that shows you on the screen current Moon phase and % of illumination.