Trigger custom script on specific log message
AirServer implements a basic AppleScript interface which can tell you if AirServer is in use by calling:
osascript -e "tell application \"AirServer\" to inUse"

Another approach is create a basic app which monitors AirServer's notifications using NSDistributedNotificationCenter:
com.airserverapp.MirroringDidStart, com.airserverapp.MirroringDidStop,
com.airserverapp.AudioDidStart, com.airserverapp.AudioDidStop,
com.airserverapp.VideoDidStart, com.airserverapp.VideoDidStop