I would download the Frugal app if I was someone with an Apple product such as an iPhone or iPod Touch.

Why?

This application allows for you to compare items (not just two, but as many as you need to compare) and gives you the best deal between the items being compared. You enter the price, the count, the quantity and the units. After that is done, you click on the arrow in the upper right corner and add a second item. You do the same for the second item and if you're done, you click on Done. It'll then give you the best price and best item.