BG Defender (Based on AB Defender) gives you a little movable window with buttons to announce the number of incoming enemies at the base you're defending in most battlegrounds. There are also buttons to call for help or announce the base you're defending is safe. BG Defender will automatically pop up when entering a battleground and close after you leave.

– www.curseforge.com/wow/addons/bg-defender/files/840031

This addon was originally created in 2007 as "AB Defender" (Arathi Basin Defender, which was the only capture the flag map at that time) and has been continued by others since then. Thanks to the community it is available in english, german, french, spanish, russian and chinese. Thanks to everyone keeping it alive!