I propose two new constants for the llGetAgentInfo() function.
AGENT_VIEWING Returned if agent has video streaming activated.
AGENT_LISTENING Returned if agent has audio streaming activated.
With such a mechanism, a media playback control script could detect if an agent interacting with it has streaming media enabled or not.
Another use would include being able to send out targeted reminders to agents who have streaming media disabled when they arrive at a theater or dance-club during a streaming media event.
I've been building/testing parcel media control scripts lately and I've noticed a pattern of confusion when people forget (or in the case of newbies have no idea) that their media streaming playback is deactivated in their client.