A core concept of this index site is that its content be available to plugin authors (e.g. to implement updating capabilities) and other websites (e.g. to implement search tools) through both RSS feeds and an API.
To enable this, I just added two API functions to the site. One allows you to extract all meta-data for a single plugin as a JSON-formatted response. The other allows you to get the current version number of a plugin. Both can be accessed by simply supplying a plugin’s ID as a parameter to a URL.
These functions could for example allow a plugin author to implement some form of update checking into their plugins. One way to do this would be to add a webdialog to a plugin that checks the version number stored in SketchUp’s extension system against the version number extracted from this index. Feel free to suggest other uses in the comments below, of course.
You can find more information here: http://sketchupplugins.com/api/