It’s the iPhones infrared part of Face ID. It flash an infrared picture every so often looking for a face. That’s my guess.
Niles infrared repeater and iPhone 13 pro
I have a Niles RCA-TT2 infrared repeater in use with one of my systems. Over time I noticed the receiver’s blue light flashing from time to time and finally narrowed it down to when my iPhone is in the proximity, even if it is locked w a black screen, it causes the Niles receiver to flash blue. Any thoughts on what is happening here?