It works i've tried. I have galaxy s4 and an Ipad. I log into both games with the same username and pass. Then say you have 500 rubies to spend on one card. IF you spend the ruby medals on both devices at the exact same time it will give you a random card for whatever you were trying to get. So say you wanted Wheeljack, you have your 400 medals saved. You log onto both devices at the same time. then you click the bridge for him at the same time. Then you click activate or whatever it is at the same time quickly and you will spend 400 on two cards instead of 1. 

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