Joe Kissell on the annoying habit of getting calendars alerts spread out across all your Apple devices at roughly the same time:
Ultimately, I would like to see a system of cascading alerts. My devices make their best guess about which one is primary at the moment, and display any alerts on just that one device. If I dismiss an alert there, that’s the end of the story. If a few minutes go by without any action from me, the next-most-likely device displays the alert, and so on. But regardless of where I ultimately see that alert, explicitly dismissing it makes it disappear from all my screens.
I like that idea and think it may be the most simple from a users perspective. I always thought another way would for Macs and iOS devices to somehow know (maybe by WiFi network) when they are near each other and only sound the alert once.
This is a really tough problem to solve for Apple, but I think we can be assured they are working on it. If evidenced by Messages on the Mac alone. When you are iMessageing you don’t get alerts on all your devices under very particular circumstances — that’s Apple’s acknowledgment of the annoyance factor that comes from multiple alerts. And Messages largely works in a very similar manner to what Kissell is suggesting.
So if you want to know the direction Apple may take with calendar alerts, I don’t think you need to look any further than Messages on the Mac.