Launch an app from within another (iPhone)

Question

Is it possible to launch any arbitrary iPhone application from within another app?, For example in my application if I want the user to push a button an

Answer 1

In Swift

Just in case someone was looking for a quick Swift copy and paste.

if let url = NSURL(string: "app://") where UIApplication.sharedApplication().canOpenURL(url) {
            UIApplication.sharedApplication().openURL(url)
} else if let itunesUrl = NSURL(string: "https://itunes.apple.com/itunes-link-to-app") where UIApplication.sharedApplication().canOpenURL(itunesUrl) {
            UIApplication.sharedApplication().openURL(itunesUrl)      
}