This is a simple one, trivial almost, except for security.
Let us put a URL in the description field for a notecard. The SL *client* will fetch the URL and display it in *plain text* inside the notecard, every time it's opened.
Make it work only if the notecard is read-only, to keep the user from hitting save and loading down the asset server unnecessarily.
DDoS possibilities? Probably. But maybe not insurmountable. HTTPRequest has potential DDoS problems, but that's already in preview.