A set of extendable classes that allow the creation of a remote API.
The Lazy Loading Widget example is a basic use case for this script. It's UI is still not very tuned, but should give an impression on what can be done with this remote-api.
When you visit your widget administration at
/wp-admin/widgets.php you'll notice a widget called "Remote_API_Lazy_Widget". Drag it to one of your sidebars where you would like to have some asynchronously loaded widget appear and give it a Title. Then reload the widgets.php page.
A new sidebar should appear in which you can drop other widgets. The widgets you'll drop in this sidebar will be loaded asynchronously via a ajax request in place of the placeholder widget.