Lately we've moved to Zulip as our main company IM app.
The story behind Zulip is that it was created as group chat application optimized for software development teams and later on (around 2014) acquired by Dropbox. The development of the core application ceased due to harsh competition from Slack. On Sept 25, 2015 the original Zulip team decided to open-source the project and make it publicly available.
Zulip has some clear advantages over the pure internal jabber server, the main of which is the web client access and no configuration to hassle with (other features are listed here - https://zulip.org/features.html)
Zulip's Android app has not been updated since Feb, 2015 and probably will never be so we took the code and refreshed it. On the plus side - it works with our internal IM server, the design has been slightly refreshed (although almost no material design is present there).
With the current version push-notifications are switched off so there is no battery drain and the IM doesn't bother you until you open the app to have a chat.
In future versions push notifications will be present ONLY as an option.
You can download the app here:
The source code is available here: