If the phone is close enough like next to her/him that would make me feel uncomfortable. Especially if it is face up so the therapist can "peer" over to look at the screen. My therapist has it on his desk and he sits away from it. It is on silent.

"ETA... during the session I got quiet, so she then started yawning, and then grabbed her nail file and started filing her nails during my session. At the end, she picked up her laptop, and started typing away on it. That was my cue to leave."

That sounds like a horrible therapist, I would advise to switch if you can.