As Kevin points out, URL Schemes are the only way to communicate between apps. So, no, it's not possible to launch arbitrary apps.

But it is possible to launch any app that registers a URL Scheme, whether it's Apple's, yours, or another developer's. The docs are here:

Defining a Custom URL Scheme for Your App

As for launching the phone, looks like your tel: link needs to have least three digits before the phone will launch. So you can't just drop into the app without dialing a number.

Answer without file rename

Note that an answer that does not require file rename is below.

Answer with file rename

OK, here is what I found, took me a bit of hunting after reading this post, so hopefully this answer will help everyone:

1.In the project contents pane at left, click the Folder icon.

2.Select the top-level blue line representing the project.

3.If you don't have the Inspector pane (right pane) open, click the button to enable it. This is the third button in the "View" toolbar towards the upper right corner.

4.In the Inspector pane, click the little folded-corner paper (file properties) icon.

5.First thing is Project Name. Type in a new one, you will be prompted to rename project content files.

I should add, this will leave your old app with the original name in the simulator, so you still need to delete it from the simulator. Also any files you created in the old app bundle will not be brought forward to the new bundle (unless you find them in Finder and move them over).

(EDIT:) One more important note. Renaming your bundle will mean that the App Bundle Identifier you registered with Apple Provisioning Portal will no longer work for that app. You will need to generate a new App ID and Provisioning Profile in order to distribute your app to a physical device.