The reason I ask what you will be using it for is to determine which set of features you need. If you're going to be using it for simpler activities, don't go all out for a Black edition with a 60fps, 1080p cam (all HERO3's are 1080p, anyways). The reason the Black Edition is so expensive is because of the crazy quality it has, and if you're using it for a more simple basis I wouldn't worry about the difference. The Silver or even White is perfectly fine for you. The main difference between these two is the white's camera has a 5 megapixels with 3fps burst while the silver is 11 megapixels with a 10 fps burst -- is that worth $100 to you?
What GoPros are compatible with the app?
Also note that their newest line of cameras, the HERO3+ (plus) are only smaller in size and lighter in weight. As of now, the Black Edition for both Hero3 and Hero3+ are only a few dollars different in terms of price, so go for the plus! And now that the HERO4's are out, check the prices of previous versions as they'll be dropping slowly. Unless of course you want the newest of the new, check out their HERO4!