>This will make people even less present, because they'll be even more tightly connected to the invisible communication happening while you're talking to them.

This is an insightful prediction I hadn't considered. People oftentimes have their phones on silent because they don't want to be bothered at certain times, or can at least ignore some intermittent buzzing. The ease of checking your wrist at every buzz will make it more tempting to divert your attention to it. While it may save phone pulls, it will increase distraction from the task at hand. Now not only do I have a choice whether to check the notification, I now know what the notification is and have to decide whether to act on it or not. Surely that added multitasking will make it more difficult to concentrate.

Just like studies they've done on emails, it's better to let them pile up for a period without notification than to quickly glance at each incoming email. People are just better at concentrating on one thing.