Nym, you inspired me.
I tried a little theory just then and got an amazing effect
(first attempt)
applied a gradient overlay to the background layer and removed the white (made it transparent). I then separated the gradient from the base layer and clip selected it (drag a select box and shift it slightly). I went back to the source layer and cut out the shape of the house from the selection and applied Gaussian blur to the selection. I went back to the gradient layer and removed the selection from the gradient and changed it's blending option to "color" then bam, instant grayscale dof.
