As voice recognition software becomes more powerful, it's quite likely that phones will be able to convert a conversation into text in real time and offer related information, including links to maps, events, email messages and even ads.
In 2008, Google's AdSense blog posted an April Fool's Day joke about AdSense for Conversations, "a new type of monetization solution that puts the 'context' in contextual advertising. In just a few simple steps, you can begin displaying ads that are relevant to the topics you're discussing -- in an unobtrusive screen above your head. Anyone taking part in the conversation can hit the ad with their hand to immediately take advantage of the product or service being offered."
{ via Jérôme Flipo }