Phone courtesies

We sit together at meetings, over meals and drinks, hanging out. Phones are on the table, blinking and buzzing with incoming communications.  

What does it mean to stay present? Does it mean they never come out in the first place? Does it mean we apologize for typing and reading? Does it mean if we take a text or email we ask if it's OK out of courtesy and share the nature of interruption?  

It's reasonable to expect that as personal tech migrates to watches and other wearables, these questions of etiquette will continue to call for conversation.