They could create applications for the other projects as well. It is common for several news sources to create applications. It would be nice for Wikinews to have one too.
Topic on Talk:Wikimedia Apps
There's a Wikimedia Commons app that's developed by volunteer developers: https://commons.wikimedia.org/wiki/Commons:Mobile_app
Likewise, I think a Wikinews app is far more likely to happen as a volunteer effort than as a Foundation project, unfortunately. The existing apps are open source, of course, and anyone could build on them.