Gnomes wearing spy outfits can find out many things.
The SpyGnome is lurking just behind you, in the shadows. He has no new information for you at this time.//
Until you install it!
SpyGnome uses AceComm-2.0 and LibRockComm-1.0 to query the addon versions of the people in your group. It can query the versions of any addon you have installed, so you can see at a glance who is running a raid status addon, boss mod addon or anything else.
Please note that it only works if the other people in your group have either AceComm-2.0 OR LibRockComm-1.0 embedded in one of their addons (many addons use these libraries).
The tooltip in the screenshot looks a bit cluttered, the version strings have been cleaned up in the latest version.