I ordered a set of Perfect Pushup devices to try them out and have been fairly impressed. The included exercises are pretty basic -- normal arm width pushups, extended arm width pushups, and hand close together pushups -- and the idea behind Perfect Pushup is to promote a natural rotation in the pushup motion to reduce or eliminate muscle strains and muscle damage.
The first time I tried the devices, I couldn't really feel that much of a difference between using the devices and doing regular pushups until I stood up and could feel how I had worked my muscles much more effectively than with the normal pushup motion. I've been using the devices for the past few days and it seems like I can add 5 or more pushups to my reps on a daily basis. I don't buy into the whole "train like a Navy Seal" or the turn into a professional bodybuilder in 30 days bullshit, but the product seems to work very well.
Unfortunately the devices are bigger than they look, so they do not travel well, but, with that said, they are supposed to be releasing a travel edition soon:
Assuming that the travel edition works as well as the home edition and is as low-profile as it appears in the picture above, it may join the resistance bands that I travel with as part of my "travel gym."