Ahh, I see. This may be a bit of a limitation with Qt itself at the time. With iOS, it seems that adding the following keys to the plist makes it work. This is true if using Xcode 6, which AppStudio currently is. If using Xcode 7, there are new things you need to do.
<key>UIBackgroundModes</key>
<array>
<string>location</string>
</array>
For Android, you need to add the following into the manifest
<meta-data android:name="android.app.background_running" android:value="true"/>
The issue seems to be that with Android, if your app is ever backgrounded, it appears that the OS can decide to suspend the app to save battery, and if this happens, the collection would stop. This would require Android services, which are not yet supported in Qt. It looks like Qt is bringing in support for Android services with 5.7, though.
-Luke