How do I allow mobile specific popups vs. web?

Hey Guys,

I am using a responsive theme. How do I get PopOver to NOT show mobile users my regular site popup (it's sized too big for mobile), and show mobile users one designed for mobile?

Is there a conditional I can use?

I tried using "if(is_mobile):" in the PopOver settings, but it doesn't seem to allow php, even though I'm using the ExecPHP plugin (which allows php in post content).

Thanks