Ted's PVP Spelltimers provides audio and visual alerts in the form of a countdown to track player cooldowns. Currently only defensive cooldowns are implemented, but this may be extended to offensive cooldowns in the future. Originally I was using a WeakAura to track these, but as I added more and more spells it became unwieldy. The outcome: one addon that can replicate what required many WeakAuras. And why not share it?
