If you are trying to add a lot of pure chest strength (instead of stabilizing muscles and core) then you should try weight vest push ups. (fitnesswayne.com)
The function of your pecs is to draw your arms across the chest, and this is the exact same movement that makes up dumbbell flies, which is why this move is noted for helping build real, functional chest strength. (fitnessandpower.com)
The landmine can be effectively used for building chest strength and muscular development. (ptinto.com)