The Sliding Push-up Bar
Want harder pushups? Make your upper body muscles work harder by introducing instability to your pushups, maximizing your range of motion, and hiting your muscles at varying angles with the Pushup Extreme.
Rollers at the bottom of this innovative pushup platform allows it to slide on the floor, making it possible to do moves that are very hard to do without them especially if you've not developed a significant upper body strength.
The Pushup Extreme is an interesting push-up bar because it can slide, allowing you do a variety of moves other than the different varieties of push-ups you can do with them.
Unfortunately, it did not receive enough funding on Kickstarter and the project was cancelled.