CDSpy is a tool to announce when important cooldowns and abilities are used in combat. It has an extensive database with most important cooldowns and abilities already programmed, focusing on healer and tank cooldowns.

Examples:

When a shaman dies, it'll announce if they have ankh available (and if/when they use it)
Who cast bloodlust?
When a tank (or pet) uses taunt [useful in LFR]
When a healer casts Guardian Angel or some other big CD
When a tank uses a big CD (like Metamorphosis, Shield Wall, etc)
When someone drops a feast, repair bot, etc
When a DPS uses Innervate on someone

A specific example, with a healer casting Pain Suppression on a tank:

-HealerA casts Pain Suppression on TankB

-HealerA's Pain Suppression fades from TankB

or self-cooldowns:

-TankB casts Shield Wall

-TankB's Shield Wall fades

You can pick the channel for the output messages, and customize whether or not the addon announces abilities in LFR/LFD, or whether it announces Taunt-like abilities.

Calling "/cdspy" will open up the options panel, which is also found in the generic Addons options page.

Options:

Override - enable announcements in ANY zone (for testing), defaulting to the Raid output channel if in a non-instanced zone
Debug mode - announces all events to the local text log for testing (not a particular channel)
Enable Global announcements - this is your quick on/off button for the addon without disabling it entirely
Enable Taunt announcements - this toggles announcing Taunt-type abilities
Enable LFR spamming - should the addon be active in LFR? Note that Override will... override this.
X Output - you can pick what output to use for Raid, Party, and LFR/LFD chat. Setting to "CHANNEL" and manually typing in a channel name (the text name, not the channel number) in the appropriate box will let you output to custom channels.