iPhone enhancment for accuracy

[+Rayswrld]

I am closing in on 1000 finds and have done all on my iPhone over the past fourteen months, that is except for the ones where I have been caching with a friend and he has made the find. A few days ago I came across a review of three items that can enhance the accuracy of the GPS capability of the iPhone. I have tried but can't find the review and don't remember names of units or add ons. Does anyone know what I am talking about? LOL! One is a thing that plugs in at the bottom of the iphone. Another is a waterproof case that enhances accuracy. I will admit that the accuracy of my iPhone is sometimes lacking and would like to make it a bit better without having to go out and buy a GPS unit. From what I recall the reviews were on the positive side so I would like to look further into it. Any thoughts would be greatly appreciated. Thanks.