This script pulls all the running containers for a given Docker server and builds a service group that contains all the public ports. Each time the script runs it will check for container services that are no longer running and remove them from the services group. This script requires that the Docker Server API is enabled. I followed THIS example to enable the Docker API on port 2375.
I will be working to add support for multiple Docker Servers in a future revision.
Running Containers inside Docker Server
Example rule using the created "DockerServer" object and "DockerContainerServices" group object
Service Group Objects that gets updated each time the script runs
Enjoy