DNA partially unraveled

Can't tell you all of it, but "living" and "kitchen" are both rooms that have 7 letters.  Between living and kitchen, he said "any one." Might be part of it as well.

And with Amanda, he showed fingers "over and over again in your mind" showed a 1, and "I really hope we get this" showed a 5.  Might be coincidence, and he got lucky he didn't need both hands. :D  (The 4, I believe was during "Just say this person's name" with the pinky folded down, but it's hard to tell with the camera  angle.)

As for the shirt, when the one fellow leads Simon onto stage (and has his back to the audience), you get a brief shot of him touching his chest.  Either they have really high-tech t-shirts or it was just a panel mostly concealed by their jackets.  As for the fellow on stage, I'm not sure how/when he does it as the camera doesn't show him during that time.  However, with the audience distracted by getting Simon up on stage, there was plenty of opportunity.