There's a difference between a full-featured multi-screen native-feeling app implemented in a webview with Phonegap and a wrapper around an existing web site. You can do a lot of interesting things in a webview and come, for some purposes, reasonably close to a native look and feel. The previous comment was right to warn about Apple's policies.

(I spent some time playing with Phonegap but it was two years ago and a simple app took 30 seconds to launch on an iPhone 3GS. Probably significantly better now, and faster as hardware has improved.)