"When will Skype open access to their codecs?" Doc Searls asked me at the Always On picnic. It's not clear they will. If they do, the Jerk-O-Meter is an example of the kind of application you could build. A project of the MIT Media Lab, it analyzes voices during the call, telling users how much they are paying attention. Per their project page, "The current version of the application runs in Linux on the Zaurus VOIP phone. It uses Ron Caneel's code to extract the activity and stress levels in real-time."

The Skype API doesn't expose the audio stream; you must work through the operating system to get at it. The same is true of the upcoming Skype Video.

There's money in analyzing and transforming media streams, whether for call centers (like the Jerk-O-Meter), annotation services, call/video quality boosters, semantic content detectors, translators, relay services, or simple stress/lie detectors. The Skype API should safely expose the media streams, and provide mechanisms for user authorized manipulation and substitution of that media by a friendly application.

It won't be easy, but the market value is huge.