We are currently seeing a problem where mobile devices that surf to our website don't seem to get picked up, not with page view or in realtime or in the events tracking. This all happened since March 15th but we are only now really starting to notice it. Debugging the analytics code snipped based on this https://developers.google.com/analytics/resources/articles/gaTrackingTroubleshooting was no problem on desktop but how do you do that on a mobile device. Android Phone or iPhone. Is there any way to debug the tracking code on the phone to make sure it works? We had been successfully using ga.js with async syntax without problems for a good long while.
For testing on iOS 6 and later you can plug your iPhone into your desktop and use your desktop version of Safari as described here by Apple. You can then see the results of the ga_debug.js.
Android has a similar tool, however, it does require you to install the Android SDK.
I'm not too sure about other phone operating systems, but that covers the main two in your question :)