Comparison Shopping
Like most smartphones, the iPhone is great while shopping. The ’sale’ item you are looking at in the store may have a $100 discount, but is that lower than Amazon? A quick way to find out is to use Amazon’s mobile interface. Better still, you can read customer reviews, although some of those can be misleading.
A site that has an iPhone interface is iSave. This will bring up prices from different online stores, so you get a good general range of what the product should be selling for.