When I say "excuse myself" I guess I really mean from any significant conversation. I may continue to spend time with people who behave like this, but I back out of any serious discussions if they are conducted with interruptions from personal devices.

Smalltalk is easy and requires very little thought or concentration anyway, but I no longer give my full attention if it is not reciprocated.

I don't make a point of doing it, but if I am left hanging mid-word while someone checks their phone, and they subsequently attempt to pick up the thread again, I just change the topic to a bullshit one (How 'bout that game on the w'end?).