Notice: this is an emulation of an iPhone Safari in no way. This tool might help you to test "responsiveness" of the layout (media queries) or you might find it useful to see the webpage in this specific dimensions (viewport) and surrounded by the beautiful body of iPhone 3. But for serious testing just get an iPhone, the iOS SDK or any other viable solution I'm not aware of yet.
Problems: vertical scrollbars narrowing the width, meta-viewport tag is not interpreted, flash and :hover events does work, horizontal orientation is not implemented (yet) etc.
Open this site in Webkit (Safari, Chrome) and set your user-agent to iPhone to make it work at least a little.
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)