Smart contracts will contact the physical world in a similar way that the Internet calls the physical world.
The Internet doesn't call the world: the world watches the Internet then acts.
Similarly, the public Ethereum network and blockchain will not call the world: the world will watch it then act.
Smart contracts can trigger events, and those that are watching for those events, will get notified.
A global system doesn't try to contact everyone and everything in the world. It's global because it allows anyone and anything to watch, interact with it, and act as they desire.
There will be services that make it easier to watch for events that one is interested in. Oracles are more for the other direction:
How can an Ethereum contract get data from a website?