Sure, but with any device that's doing security correctly right now, the only thing you get to control is whether you let it connect to the service it wants to

Sure, but with any device that's doing security correctly right now, the only thing you get to control is whether you let it connect to the service it wants to use or not. It's not like you can re-target it connection and choose which types of calls make it through and which don't. And at that point you might as well just choose to not plug it in to the network (or give it your wifi credentials or whatever).