Synack is a client/server wrapper for https://github.com/alloy/terminal-notifier that allows arbitrary messages to be sent to Mac OS X Mountain Lion's Notification Center.
Note that Terminal Notifier must be installed in your Applications directory for Synack to work properly.
To start synack:
To send a message to your local Notification Center:
synack -m "Watson, come here, I need you."
You can send messages to remote machines by specifying a host and port in the client:
synack -h my_remote_machine -m "I'm here, what did you want?"
You can even use UNIX pipes to send messages (first line of input only, for now):
echo 'Foo to you, sir.' | synack