SmartNav Hands-Free Egronomic Mouse
SmartNav is a hands-free mouse system that is developed by NaturalPoint. It works by using an infra-red camera to track a reflective sticker that you can place anywhere on your body. SmartNav is generally marketed to persons with disabilities, but it is a great hands-free just about anyone.
The reflective sticker is just one of many accessories that can be used with SmartNav. Some of them include:
There are also several options for clicking. There are left and right click inputs for various ability switches, hot-keys for clicking, and dwell-clicking by hovering the mouse over an area for a certain amount of time. I personally use a click-switch for left-clicking, along with an on-screen keyboard. Here is a YouTube video demonstrating how it works: