Love it! I was thinking of migrating off GAE for this reason, but now will re-evaluate.

One feature request - can we add a URL parameter to the firewall rule? The idea is I want to restrict access to certain URLs to a well-known set of IPs - e.g. I don't want login into admin pages unless coming from a known IP. Is this possible on GAE right now?

I know I can split the service into two (restricted and public) and then firewall the restricted service, but wondering if there's a simple way to parametrize firewall services by URL.