Here is a review. http://www.treotoday.net/2009/03/04/kindle-iphone/
I am not sure about having to own a Kindle, Harry. Where did you find that? That would be a bummer, really. If that is true, they should offer a mobi reader for Iphone, as it would be the same software, essentially.
the reviewer even expressly states that it is possible to get books on Amazon without a Kindle