How should I slice buttons for ios development

I'm going to slice given image for iphone developer. Since I'm front end developer and know that this button can be created using CSS in front-end development I don't have any idea about how should I proceed? May I give PSDs directly to developer or it should be sliced. If it should be sliced then how will it be

http://ift.tt/1DbP5oY

Please note this button has gradient, rounded corners and little downward arrow. Forget the text inside for now.

Have iphone developers ability to do that type of stuff using their code?

If I should export those buttons (eliminating the text / icon inside ). At what resolutions that should be?