I don’t know of anything that is pre-built but there are many ways to control access to the server. You can send parameters through the NetConnection.connect(url, [params…]) method to the server side onConnection method. This is described in the User’s Guide. Also check out this post:
MultiMediaCart is a secure online shopping cart for the sale of pay per view / pay per minute content, including streaming video, music, and live events. It has built-in support for Wowza Media’s Secure Token anti-piracy technology and many other features.
Paste the URL of the media file, set the price and it is ready to sell and deliver on demand. It is a hosted service with unlimited storage and bandwidth for your site. It acts as a secure gateway for any streaming server - Wowza, FMS, Windows, Real, iPaper, etc. It supports pay per view and pay per minute (also free content).
Anybody can publish a live event or video on demand, music listening or ebook viewing site – instantly. It was designed especially to provide secure delivery of all media formats, but it supports all languages, currencies, payment methods, taxes and shippers. One feature that is helpful for large video libraries – it has a timed preview feature, native bandwidth detection, user-restrictions, IP tracking and security, management reports, with real time monitoring and control. Go to http://www.MultiMediaCart.com
Using logs you could also bill for time (PPM) and/or bandwidth.
Other approaches involve using user authentication in a Wowza application module, then the IMediaStreamActionNotify3 and a JDBC connection to log usage.