Emerald Chronometer is a very expensive watch, or really a bunch of watches, emulated on your iPhone. It's an amazingly sexy app.
The app includes emulations of 7 different phones -- each with 2 different faces (front and back). Extra features include the ability to set the time for each watch, night mode on some watches that give the watch a luminescent glow, and great help for each individual watch.
The interface for each of the watches is just fantastic. Absolutely beautiful in every way right down to the scratched back of the pocket watch. While I question the number of times I will go back to this app, it sure is pretty. Would be nice if Apple would allow you could specify an app to run as the background on the lock screen instead of a static image -- I would choose this one.
In the end this is the kind of app that really serves no great function over what the iPhone internal clock can do. But dammit is it cool!