Whilst that might be cool technology, I wonder at the user experience and confusion when my mum clicks on the phone icon and all of a sudden this menu appears asking me whether I want to use the phone or skype (obviously I get that the call can be done with either, but mum probably doesn't).
If your mother doesn't have skype installed she wouldn't get this message. If she does, I would presume she knows what skype is for.
Additionally for the big system-level intents there is an "always use this action" which is useful so you don't have to repeatedly tell it to use the phone app to place phone calls.
The iPhone experience is that the system Contacts app is only for calling via the phone system. If you want to call via Skype, you open Skype and then use its embedding of the system address book. It is really quite clunky.
