Doesn't the Motorola app Meeting mode silence everything?
So I use this too, and it does silence the phone, but for meeting mode to kick in, you need something in your calendar, such as an appointment etc. And the calendar needs to be selected (in moto assist settings) so that Moto Assist can read it.
Mine is going in and out of meetings, silencing my phone all the time (my calendar has many events) but sometimes you just have that spontaneous moment in the day where you need to silence due to a certain circumstance or you simply didn't add that appointment into the calendar for it to know to silence it.
To create calendars (similar to gmail labels), go into gmail on PC, then click on apps top right, go into settings, there you can create different calendar names. For instance, I have a shared calendar with wife called "dr appointments", and every event we add to the calendar which is a doctor appointment, we simply add a tag or I should say use drop down menu and select " dr appointments "
You can also add calendars which are already set up such as US holidays, Facebook events. Let's say there's a specific sports team you like ,if they have a schedule which was made public, you can add that to your google calendar and keep track of where and when the games are.
(You may already know this, but could be helpful to another person not familiar)