I'm suspicious the answer to that is going to be "no" -- the 700's search and annotation functions seem to rely on a virtual keyboard with touch-screen input. That's not possible on the 505, of course.
In order to implement some proxy using the existing hardware buttons on the 505, it would be necessary to re-write the interface.
I think
Sony could probably pull that off (assuming there aren't any
other, less visible hardware limitations in the way
), but it seems to me that anybody
else would have a rather tough go of it.