[ros-users] Callback for new topics?

Hey,

Is there a way to receive a callback or notification when new topics appear?

I see that rospy has this function:
http://www.ros.org/doc/api/rospy/html/rospy.client-module.html#get_published_topics

However, I'd prefer not to be polling it. For the moment, I've configured my
system with a shared "announce" channel where new hardware can make existing
hardware aware of itself and what its topics are. However, it would be great
if it were possible to simply subscribe to a topic of new topics, and do it
that way.

Thanks for any input,

Mike