Android service using components from other applications

I'm trying to write an Android application that will use plugins. These plugins will just be other Android applications without a launcher. For instance my application can fire an intent saying "I want to get a list of images". Then, the user can pick from which application he/she wishes to find the list of images (typical facebook-plugin, flicker-plugin etc.). The choice the user makes may or may not show an activity, but it will return the list of images to the application. However, this 'list' of images, isn't just a list of URLs to the image itself, because some sites which the user should be able to get the images from needs parsing, and that takes time, rather it's a resource as of h开发者_JS百科ow to obtain the list of images, so that later, I can connect to a content-provider that will download the images needed on the fly.

However, I also have a service running that gives the user the ability to mark a given set of images (like a chapter, or album) for downloading, and then the service will download the images specified, but my application doesn't know how to get images from flicker/facebook/any other plugin, so I was wondering how I can make my service "talk" to the plugin to download the images in the background (without having to fire an activity that the user needs to see).

Any thoughts of how this can be achieved would be appreciated.

PS. Sorry about bad English, not my native language.