Is there any way to get the installed apps on an iOS device? I know that is not possible with iOS 5 or earlier but maybe iOS 6 provides some info about this?
If that is not possible, the only way I think this could be done is trying to get the URL scheme of the apps and check if they are installed. Is that correct?
Also, to launch an app I should use openURL: from UIApplication, right? If that is the case, I need to know when the app that I launched is finished or wants to be closed, so I can show my app; is that possible?
No there is no API to check which apps are installed (you could have checked this in the SDK documentation).
You best guess is to use the URL scheme to check whether know app are installed. The only way to launch the app is by its app URL scheme and there is no way to check wether the app is launched and there is now default way to ask the other app to re open your app. So you are left to the mercy of the other apps developer if they have build such an option.