See this thread from August 2014 for current debugging possibilities.
With SmartGWT mobile, you'll only have Super Dev Mode. As you should choose Chrome over Firefox with SmartGWT mobile, you'll basically have to use Chrome.
Note that debugging takes place in the browser and not the IDE with the current Source Maps support.
I can't help here as I neither use Super Dev Mode, yet, nor mobile.
The FAQ, perhaps a SmartGWT mobile sample and general GWT/SuperDevMode forums should help.
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