This addon lets you input guild names and when a member of one of those guilds appears, you are alerted in chat.

Features:

Use /guildgrudge or the interfaces button to open the addon window
Add in guilds by name, optional note can be included.
When members of that guild appear nearby, you will be told in chat their guild, name, and class
Additional options for auto-rivaling any member of that guild, reporting to /party chat, and playing a sound.
1.1: One minute timer for alerts about the same person.
1.2: Target an enemy player and the next time you go to add a guild to your list, their guild name will be auto-filled in the name box.

Known Issues:

~~If a player goes in and out of range repeatedly, the chat reports can become spammy, as well as with stalkers going in and out of stealth. I have a planned timer to fix that, but it is not in yet.~~ Now on a 1 minute timer.
Let me know here if there are any other issues

Potential future additions:

Distance/direction indicator is not going to happen. I tried it, and the UnitCreated event parameter usually says an enemy player is at position (0,0) so I won't be able to get reliable information for this. If anyone has any workarounds, let me know.
Detecting if a guild input is an actually existing guild or not. Currently when you add a guild to the list, it just accepts it. I have not found a way to check if the guild name exists or not.
When in your capitol city, any enemy player will trigger an alert, regardless of guild.
During development, a guildie mentioned that any guild that is "_____ Gaming" is probably all assholes anyway, so maybe I'll put an option to handle any guild of that pattern. Probably not though, I just thought it was funny.

Thanks for checking out my addon, I'm Blazz on Warbringer.

GuildGrudge