Could well be true
I wrote software with hidden stuff in your emails
Code embedded in a single white pixel on your screen
Nothing nefarious in intent but we could gather certain basic information
Because it was embedded in a single pixel (or multiple pixels, graphics) you’d have no idea that it was even there
I had my phone off during this and when I just turned it back on I got 4 alerts minutes apart in a row. 20 minutes after the initial alert. The 2nd, 3rd and 4th ones came even after I didn’t click “OK” on the notice and had deleted the original text on my phone.