The ProScope Micro Mobile is an add on for iOS devices (available for (iPhone 4, 4S and 5, iPad, and iPad Mini) that puts a microscope lens over the device’s camera. It can give you 20X to 80X magnification for whatever you’re looking at. The clarity and detail it passes to the screen is amazing. If you want to get a closer look at items around you, this will bring a whole new world to your screen.

I ordered one of these for a work application and was very disappointed. At first I thought I was unable to focus at higher resolutions, then I realized that what you are buying is a 20x lens and then you are blowing up the picture digitally to 80x at which point, you lose any detail. There are no measurements, but I would say the picture loses any useful quality before you get to 50x. Basically, it is a pretty toy and not much else.
Great idea! Just not practical. If they gave you a 50x lens and you could zoom in or out from there, it might be a better investment. There are other products out there that deal with this issue in a better way.