Tobi has displayed the ability to be able to accurately locate and teleport to any other character (He displayed it with Naruto, Sasuke, the sealed Gold and Silver brothers, and more).
How does that work? I don't recall the Sharingan having such a wide range.
That ability is explained in later episodes, so it will be enclosed in spoiler tags.
When Obito crashed onto Madara's cave, he saved him by attaching a white Zetsu (who is a clone saturated with Hashirama Senju's cells). There are many white Zetsu clones spread across the land, and they can communicate with each other via the roots of trees in the earth. (Avatar: the Last airbender style). The Zetsu attached to Obito is no different. That way he can get immediate intelligence from practically anywhere, including the location of other people.
The teleportation is made using his normal space-time techniques.