You've probably seen plastic bags filled with water suspended from string at some point in your life, on a patio or outdoor seating area at a restaurant. The movement and amplified color produced from the refraction of light on the water proves to be a potent pest deterrent, ushering away flies and some stinging insects.
The Anti-Fly Sphere by José de la O is a more elegant approach to the plastic bag, and certainly a greener approach to bug spray. The Anti-Fly is comprised of a glass bulb and stopper and utilizes the same concept as the bag-full-of-water in a more elegant form.
While it's just a concept for now, the idea is solid and something that should be readily recreated.