This ad-don modifies the signup list for calendar lists to indicate several statuses for characters signed up for a given event.

If the character's name is dimmed, that character is currently offline.
If the character's name has an asterisk (*) following the name, that character is not in your guild.
If the character's name has a question mark (?) then that character is neither in your guild or on your friends list.  This is significant, as we cannot tell if this character is online or not.

Planned additions for this add-on include sorting by online and guild status, and indicating the total signups / total online ratio.