The tuning that Will & Nate play it is open, I prefer to have it Capo 3rd. 
It all just depends on your vocal range. http://youtu.be/bFpEtFP9gvw <-- this is 
the video of them playing that I got the chords from. Although this doesn't 
include the higher fretted stuff. All it is, is a higher version of the chord. 
Now the chords are a little weird in this song (some of them) so here are the 
weird ones used. (these chords might have an actual name, but pardon my laziness 
that i didn't look). But I couldn't find anything else online that was right, so I 
charted it out for myself. I it helps, Enjoy! (first chart)

 B/D    G/D    B/A     D      B       A
E - x  E - 3  E - x  E - x  E - x  E - x
A - 2  A - 0  A - 2  A - x  A - 2  A - 0 
D - 0  D - 0  D - 0  D - 0  D - 4  D - 2
G - 0  G - 2  G - 2  G - 2  G - x  G - 2
B - 3  B - 3  B - 3  B - 3  B - x  B - 2
E - 2  E - 0  E - 0  E - 2  E - x  E - 0

Verse1:
D
Look behind you,

B/D
Avoid the shadows,

B
Watch your back now,

Make your breathing shallow.

D
Keep your room locked,

B/D
And leave the blinds closed,

B
I'm right there staring at your window.

Pre-Chorus:

Gsus          B/A        A 
And all I need is you.

Gsus          B/A        A
And all I need is you.

Chorus:

B/A
I'm in the background,

Gsus
On the radio,

D                         
I'm in your car, 

B/D                          B/A
In your house, 
                            
Waiting at your door.

                        Gsus
Under your footsteps,

                                  D
I'm everything you know.

B/D
Just let me haunt, let me haunt,

B/A
Let me be your ghost.

                              D
Let me be your ghost.

                                         B/D
Let me haunt, let me haunt,

                            B/A
Let me be your ghost.

Verse2: 

D
You had your chance love,

B/D
You tried to stay strong.

B
You tried to let go,

Tell yourself you moved on.

D
But then it comes back,

B/D
That feeling in your bones,

B
Like I'm right there.

PreChorus:

Gsus        B/A         A
And all I need is you.

Gsus        B/A         A
And all I need is you.

Chorus:

B/A
I'm in the background,

Gsus
On the radio,

D                         
I'm in your car, 

B/D                          B/A
In your house, 
                            
Waiting at your door.

                        Gsus
Under your footsteps,

                                  D
I'm everything you know.

B/D
Just let me haunt, let me haunt,

B/A
Let me be your ghost.

                              D
Let me be your ghost.

                                         B/D
Let me haunt, let me haunt,

                            B/A
Let me be your ghost.

(Repeat Last Chorus Twice)