After all the jokes about this idea! Sorry if some folks may take the demo the wrong way but it's the core idea that counts. I'm not even sure its such a safe idea; especially when the release is made ... I bet there's a chance for it wrapping around the front rider's rear sprocket or derailler. Good for a day when we should be X-skiing rather then riding on icy road margins.
Enjoy,
Norm

Link: http://www.bicyclebungee.com/