What is 人 doing in 你现在人在哪里？
Both sentences are correct. The word "人" is added to add emphasis to the physical location of the person.

You can take 你现在在哪里？ to mean "Where are you now?"

And 你现在人在哪里？ to mean "What is your current physical location?"

The former is normally used when the asker and the subject are within the same locality (e.g in a shopping mall). The latter is often used when the asker and the subject are far away from each other (e.g. in different countries).

A corresponding response to 你现在在哪里？ is 我现在在XX。

A corresponding response to 你现在人在哪里？ is 我现在人在XX。