GmailInviteTray shows you how many people already made a response to an event from Gmail. You will see in the tray how many people already said "yes". Monitor your Gmail invitations with this tool.
All you have to do is open the invitation for the event that you got from Gmail, copy the URL link and paste it to this app. From now on, you will see in your tray how many people already accepted the invitation for the event.

The license of this software is Free, you can free download and free use this email tool software.