Call tracking works with the Twilio API, so you'll need an account and phone number at Twilio before you can get started. Twilio sells simple, pay as you go phone services, sign up at http://www.twilio.com.
Installation is as simple as copying the folder, making it writeable and editing the configuration file.
Copy the folder to your server.
Make the folder writeable.
Access via browser
You'll need an account at http://www.twilio.com. Set your Sandbox phone number or purchased number's Voice URL to http://www.yourserver.com/handle_incoming_call.php. If you have upgraded your Twilio account, you can use this application's UI to configure your numbers.
Released under the MIT license.