I'm lazy person and I don't like to turn my Android phone to silent or vibrate mode "MANUALLY" during meeting. I'm looking for something that can be done "AUTOMATICALLY". Probably I get used to my old HTC diamond phone (runs on Windows Mobile) which this feature comes by default.
Anyway, I found this cool software called "Busy Me" and it gives me exactly what I wanted. I have been using this software using for quite sometime and encounter some minor bugs (sometimes it just doesn't work and I need to turn my phone to silent mode manually) but I think that is still acceptable. Most importantly, it is FREE!
I turn off the "Notifications" because I think it is a useless thing. But if you want to get a sense of whether the "Busy Me" works as expected, you may want to turn it ON to see how it goes. The "Activation" and "Deactivation" can be set "On Time", 5 minutes, 10 minutes or 15 minutes early. I set it 15 minutes for both which means that my phone will be in "silent" mode 15 minutes prior to the meeting (activation) and 15 minutes after the meeting finish, my phone will be back to normal mode again (deactivation).
Play around with it, there are other pretty cool options(e.g. change to silent mode instead of vibrate, choose which calenders to use, and etc.)
To download this software, just do a search "Busy Me" in Google Play and you can also download it from Google Play here.