Here is a motorized elliptical trainer that fits under your desk and lets you get your feet moving. The Sunny Health & Fitness Motorized Elliptical Trainer has 3 speeds and multiple modes (auto, manual, forward/background movement). Its built in carry handle lets you move the device around easily.
This under desk elliptical trainer comes with a digital monitor. Could prove useful for rehab. Costs under $160 at this time.