The reason tears are produced when cutting onions is the irritating gas released when you cut into the cells of the onion. Your eyes dilute the irritant by producing tears.
These goggles are designed to deal with this age old problem, they do this by forming a soft foam seal around your eyes, and stop those offending fumes from getting in.
This is a perfectly simple and functional kitchen gadget; I would use them at least every other day. These onion goggles probably work out cheaper than all those tissues you would use without them.
You can find these funky looking goggles at ThinkGeek, they cost $24.99.