Assist is one of the core apps that Motorola has dropped into the Play Store, which means it can be updated as needed. It's gotten a few tweaks already, and today another update is rolling out. This time it should make the meeting mode more useful for users with more than one calendar.
The meeting mode in Assist will automatically silence the phone and auto-reply to messages (both optional) when you are in a meeting. This is automatic and based on your calendar appointments. With the new update, you can specify which calendar will trigger meeting mode. For example, you can keep your significant other's calendar on your device, but have only your calendar trigger Assist.
The update is live now in Google Play for anyone with the Droid Ultra, Droid Mini, Droid Maxx, or Moto X.