The Bing Mobile Application provides access to the Bing feature set on your mobile device. I worked on the iOS flavor of the app, while at Microsoft, in late 2010 and assisted with bug fixes and a number of new features - most notably plan support.
(From the Bing iOS product page)
Bing is a decision engine designed to work beautifully on your iPhone. Whatever you're looking for, Bing can find it and help you get there-down the street, the other side of the world, or somewhere in between-Bing has the answer. Tell Bing what you are looking for with voice-activated search, even addresses, when you need to be hands-free. Bing helps you to easily find a restaurant, with the cuisine, atmosphere, and location you're looking for, in the price range you want. You can even reserve a table or order delivery right from Bing. Use the Plans feature to explore nightlife options, likes, and comments from your friends on Facebook, or use the social feature to see relevant updates from Facebook and Twitter in your search results.