in this article, i will explain how to easily create a USB drive to boot your computer from.
you can try a live android version from this USB (without affecting your installed OS)
and/or you could install it if you want.
This article explain the usage of IntentService class in android SDK to perform background processing to offload tasks from an application’s main thread (Your activity).
when IntentService jobs done, the results are sent back to the activity.
You may reach a point where you need to transfer data from a server (web-service) to a an android client. although, there are many ways to achieve that goal, one of the simplest is using JSON. JSON is better then XML in terms of small bandwidth footprint. it has a lot of libraries for every available platform, so it makes the best solution for server-client communication.