The EyePal is a new product that claims to bring the rear sight, front sight and target all into focus at the same time. The EyePal is a small disk that attaches to the front of your shooting glasses. The disk has a tiny hole, or aperture, in it that allows the eye to focus on more than it could otherwise.
As I understand it, this is the same effect that a photographer uses to adjust depth of field through aperture size adjustment. A photographer can capture a very shallow depth of field (sharp subject, blurred background) with a large aperture such as f2.8. With a smaller aperture, such as f11, a lot more of the scene is in focus.
It appears that by forcing the eye to look through a tiny hole, it allows the shooter to perceive more of the target and sights in focus. I would presume that you would need good lighting to effectively use this device. MSRP is $29.95.