Yes, I have perfect pitch and I actually find it quite useful in the arena of composition. Key plays an important role in my compositions. Certain keys have moods, feelings, etc. associated with them. Therefore, when I think of a tune, I automatically know what key it is in and I can play it on the piano immediately.
Unfortunately, I don't think that it can be developed unless a person possesses a certain genetic predisposition. I have yet to meet someone who wasn't "born" with it or who actively worked to develop it.