The Transit App, an application that provides commuters with real-time transit information on iOS, makes its Transit App API available to developers who may want to integrate the functionality with other applications. The app has already been widely downloaded and received positive customer reviews, and filling the gap that was left when Apple removed transit from its own Maps app, it seems to be a really useful tool for anyone who relies on public transportation and the ability to get accurate and timely travel information.
Twitter has started early beta testing for a new User Streams API. Currently the service is just for desktop clients, but it could eventually fuel other types of applications that need access to data in realtime. Similarly, the stream concept may be one we see used by other services.