Is it possible to add more search providers to the Google Search? In the Google Now/Search application, when you view the settings, you get a list of all the applications that can be searched.

Is it possible to develop apps that can add more search providers to this? I'd like to be able to search my calendar and contacts too but I can't seem to.

Earlier Android versions had an application called QuickSearch but this seems to have been removed as per the AOSP commits. Does Android now support in-device search or is this idea dead? 

Here's a screenshot of my settings page.



Click image for larger version
Whilst it is possible for apps to make themselves available to be searched, each applications needs to be updated to implement app indexing in order for them to show up in this list.

I don't think it is possible to add additional providers without the apps themselves being updated to support this.