there is 2 kinds of phone applications :
- you can do a jquery mobile and sure you can integrate it to your cms (xoops or any other cms). this is an example from my websitehttp://www.maitsco.net/mobile-dev/#/mobile-dev/portfolio.php, I tried to integrate a part of publisher to the app by connecting to xoops db.
once you finish, you have to go to phonegap.com to create the sdk for all phones. then publish the app the the stores (app stores, google play...etc).
- an app made by using xcode (for iphones) or objective c or javascript.
it's more complicated, but also you can integrate your cms to it.

I guess that Simon can make such work for you.