You need your Rails server to send, in real time, a notification to one specific user, a group of users, or to all connected users.
Use the Juggernaut Rails plug-in together with the
XMLSocket provided by Flex framework to allow the Rails server to send a notification to your Flex application.
For a brief definition of the concept of push technology, consider this one from Wikipedia:
Push technology on the Internet refers to a style of communication protocol where the request for a given transaction originates with the publisher, or central server. It is contrasted with pull technology, where the request for the transmission of information originates with the ...