Whether or not this would function as an actual button to a room the user is in, I'm not sure; maybe if there was an extra box to set which room people would go to if they clicked your button. But regardless, I still think it would be pretty neat to see when people are in dAmn.
The 'Show when I am in chat' option would be disabled by default - not only for privacy reasons, but I'd imagine it could save dA's servers from extra database lookups for those who don't visit the chats at all and wouldn't care about this feature.
I've always kind of had this feeling that there was something missing between dAmn and the rest of dA - like they're kind of two separate entities; and I think this would be a nice step to bridging them together more.
This isn't necessarily to expand awareness of dAmn; it's just something I think would be neat. Although, I'd imagine this would increase awareness of dAmn, anyway, as I routinely come across people who enter the room and say things like "I had no idea dA had chat!"