Users of Google's free Gmail service should be used to the idea that this company scans through their messages and serves them ads based on the content. Even this group might be concerned if they learned Google wants to do the same with their voice calls, however.
According to a patent application by this company, it doesn't intend to run voice recognition on what's actually being said during a call on an Android smartphone. Instead, Google would be listening to the ambient background noise and making judgments about the conditions. So, for example, if the service decides someone is at a sporting event, they might be sent an advertisement for sporting goods.
Another part of the patent covers images. If a new picture is taken with the smartphone's camera, a service could look at the background and see that the person is at the beach, and then send them swimwear ads.
At this point, it is not known when - or if - Google plans to implement this system. When questioned about this application, the company pointed out that it frequently applies for patents in technologies it is only considering. If Google does choose to put this into use, it will almost certainly be brought up in the on-going public debate concerning Google and privacy.