The native mobile resources module has a JS action called "GetDeviceInfo". This will give you the buildnumber of the installed app. Now all you need to do is cross-reference it with the latest build version (either by storing it in your database, of figure out your own method) and display a link to the appstore when versions don't match.
you can add button to call nanoflow and on this nanoflow you need to pass the app URL to this activity like this, if you need any help reply here