Last year a project was developed by master students implementing a chatting application for DHIS 2. This included an XMPP back-end running on the server, in addition to an Android-based client application.
There was also implemented a chat client in the browser version of DHIS 2, which connected to the same XMPP server.
The work is only a proof of concept so far, and will need to be improved in order to make it become a core part of DHIS 2.
The application that already exists is a good starting point, but you are not required to work on it. It is however advised as you use it as a reference for your work, regardless of the directions you want to take. The source code, in addition to a few notes by the developer can be found here: https://github.com/niclashalvorsen/DHISmessenger
Definition of tasks
Several improvements need to be addressed for this project. Descriptions of the tasks follow.
1. Improve data usage
The biggest problem is that the application uses big amounts of data. Because the users of DHIS 2 are typically in low resource contexts, that is an absolute show stopper. Using the existing solution or not, you are to find and implement a solution where data usage is at an absolute minimum. This could, and should be done through caching on device, in addition to other strategies you find suitable.
2. Redesign existing app to follow Materal Design guidelines (optional)
The current application has an adequate user interface. It does however not follow Material Design guidelines. There are several other official DHIS 2 Android projects that do, or are currently being redesigned to follow Material Design. The DHIS 2 messaging application will also need to follow these guidelines in order to fit in with the other applications, and to allow for a uniform design across applications. An introduction to Material Design can be found here https://www.google.com/design/spec/material-design/introduction.html