Google announced that it is making a pre-release version of the Android 1.5 SDK available to developers. This next version of Android is based on the Cupcake branch of the open source mobile platform and introduces a bunch of APIs for features such as the promised on-screen keyboard, video recording and playback capabilities, and a new home screen framework for developing widgets and populating live folders with custom content.

Google's own applications on the platform have also been tweaked to offer a number of usability and performance enhancements. For developers, applications will reportedly be easier to write and much more robust, with better debugging capability and virtual testing. You can see the full list of feature improvements here. No word on when all this will actually be available on existing Android smartphones, or if it's intended for future devices only, but the Open Handset Alliance says it will be releasing a series of articles in the coming weeks to highlight new APIs and help developers prepare their applications for the release of Android 1.5.