Google has announced AdSense for Mobile Applications which allows developers to earn revenue by displaying text and image ads in their iPhone and Android applications. They have launched a beta site where developers can learn more about the AdSense for Mobile Applications program.
In their own words, You don’t have to be a mobile expert to see how smart phones are revolutionizing our daily lives. Lower prices, faster network speeds and unlimited data plans mean that people often reach for their cell phone rather than their computer when they are seeking information. As a result, mobile applications have become more and more popular, helping people find music, make restaurant reservations or check bank balances — all on their phone.