MZ- please do work the same magic you did with the booty challenge but make it a little shorter overall. Especially the intro. Do 5 movements:

Regular pushup
incline,
decline,
wide,
narrow

when explaining incline or decline you can tell people to use a bench or a chair, wide or narrow to move their arms further or closer apart. Not all people will have gyms or benches so try to make it applicable to everyone. 

http://www.fitnessmagazine.com/workout/arms/exercises/push-up-challenge/