Let the hive mind of Engadget get that for you.
"I am looking for a device that will stream sound from one source to several recipients. For example, I want to stream sound from my TV or stereo to my phone or MP3 player that has radio and Bluetooth capabilities. I have looked into radio transmitters and they seem like a decent choice, but I can't find one that uses external power (USB or from the plug) and I would want one with a transmit range of around 50 meters. Thanks!"
Let's face facts, Sylvanas is no fool. She knows good and well that at least half of the living beings (read: most Alliance and ALL Scarlet Crusaders) in Azeroth consider the Forsaken to be inhuman monsters that need to be destroyed utterly. No matter what happens, she and her Forsaken are going to be facing attacks from living humans trying to retake Lordaeron or overzealous armies of Scarlet Crusaders trying to eradicate them as just another part of the Scourge.
The plague is designed to kill Scourge AND the living. The Scourge as part of their quest of vengeance, and the living as defense against the inevitable assault against them.