notify-push
A general purpose popup notifier sender/receiver for using WebSockets (via Pusher).
Disclaimer

Installation
Create Pusher App
Create an App on Pusher named notify-push. The free account should be plenty.
Install notify-push
For the Receiver machine and the Sender machine(s):
$ gem install notify-push
Create & Distribute Configuration File
Next, create a configuration file with your Pusher App's credentials (found on your Pusher App's page under App Credentials) and distribute it to each machine (Receiver and Sender(s)).
Location: ~/.notify-pushrc
Example
pusher:
key: a1a2a3b1b2b3c1c2c3d1
secret: a1a2a3b1b2b3c1c3c1d1
app_id: 12345
Receiver
Usage
Invoke the Receiver with:
$ notify-push --receiver # or -r
TODO: There's a .plist launchd file in there but it's not ready.
Sender
Usage
$ notify-push <message> [title] [subtitle]
Alternatively, you can curl or use any Pusher tool to send on messages to your notify-push app on channel "notifications" with data:
message: The to notify you with in the notifier popup (REQUIRED)
title: The title of the notifier popup (Optional)
subtitle: The subtitle of the notifier popup (Optional)