For people who spend a lot of time sitting definitely need some form of exercise. There have been several solutions proposed to this problem. There are even treadmill desks.
Another solution is here thanks to K-Tor. The company’s Power Box is a handy little generator that has pedals. The pedals can be cranked by hand or feet depending on your preference.
“The Power Box can produce up to 20 watts. It can directly charge a full range of portable devices. Because it is so powerful, it can charge more than one device at a time — like a smart phone and a tablet. Since it can be cranked for long periods of time comfortably, it can be used for higher power applications that it cannot charge directly. Simply charge an external battery and run your appliances, either directly from the external battery or through an inverter.” Source: Treehugger
The device has its own battery pack which can be recharged via an electrical outlet.