A simple app written in node.js (and, marginally designed to run on Heroku).

This listens for charge.succeeded webhooks from Stripe, and then prints a 
message (and plays a sound) in any browser connected to the server.

For info on setting up on heroku, see this tutorial:
http://devcenter.heroku.com/articles/node-js

Install dependencies with:
npm install .

Run with:
node server.js

Open in browser with:
http://localhost:8080

Add your stripe api key to your env:
heroku config:add STRIPE_SECRET_KEY=<YOUR KEY>

Configure your stripe webhooks here:
https://manage.stripe.com/#account/webhooks

to http://{YOUR_SERVER}/stripe-webhook