They use bots to detect keywords in text messages, but even they get thousands of false alarms. We don't have the bot technology to detect visual and audio cues, there's just too many factors, they would have so many false alarms it wouldn't matter.
You think that the government doesn't have technology that the general public doesn't know about?
They aren't going to use the Kinect to spy on you. Why would the government use the Kinect when they can just use your phone? Something that has and will give more information about you than your kinect could ever hope to.
People love to compare the Kinect to a labtop camera or a phone camera. But the Kinect is far more invasive than either of those. The Kinect is a 1080 HD infrared, heartrate sensing camera with four microphones. There have even been boasts that it can "read emotions".
Look up the news about the NSA. The Washington Post is showing that the NSA violated its rules about what not to monitor. Most were ruled as mistakes, but some violations were abusive. For example, it failed to destroy some information the Foreign Intelligence Services Court declared as illegally collected and therefore must be destroyed. With the fact that James Clapper, the Director of National Intelligence, perjured himself in front of Congress regarding privacy violations by the NSA, it is no stretch to conclude that the NSA is rogue. Also, Congress also failed its duty again by failing to impeach Clapper for his perjury.
According to the Guardian at http://www.theguardian.com/world/2013/jul/11/microsoft-nsa-collaboration-user-data, Microsoft was legally forced to give the NSA access to Skype, Outlook.com, and SkyDrive. People are scared that Microsoft will hand over access of what is captured by Kinect to the NSA as well. This will essentially turn our televisions into 1984-style telescreens which are televisions that watch you back and send your images back to the government without the option of turning it off. With the announcement that the Xbox One will no longer require Kinect, the last part has been rendered untrue. However, it required intense lobbying by gamers to do this.
This stuff makes me think of this hypothetical scenario: someone playing a Splinter Cell game on the Xbox One where one plays as a fictional NSA agent while being monitored by a real NSA agent.