What we wanted to do was display on each user profile a list of all the events users create. Especially because the url of events are generated randomly and create a url impossible to remember. To do this we had to implement the hook_menu() in a custom module, called "yourmodule" in this example. What is important is that the path "user/%user/events" (where %user is the user ID) needs to be a child of user/%user and the tab link will then be created on "user/%user" and the child pages.