The Bing Search app has been updated to include the translation feature first demoed at WWDC, as part of the initial unveiling of iOS 8 extensions.
Very simply, downloading the update adds a Bing Translate action to your Activities list in Safari. Enable the action and then visit a website in a foreign language. Pressing the Translate action in the share sheet will machine translate the webpage’s text to the system language, by default. The text content changes inline and happens very quickly.