Here is a pulley-based mini gym that fits in the palm of your hand and lets you get a workout anywhere. The Stay Fit Mini Gym lets you perform over 100 exercises. It comes with a tension dial that can be adjusted to offer 1 to 25 pounds of resistance.
The Stay Fit Mini Gym may look like a dumbbell but lets you do a whole lot more. You can use door/chair anchors and handles to do more with it.