I picked up a new app today called PaintCode. It's targeted at developers, and all drawing actions are recorded as drawing code for OS X or iOS. This is a feature already available in Opacity, but the code generation seems to be the primary reason for PaintCode as opposed to Opacity, which is a drawing program that will export what you've drawn to code.
Opacity does more. It's more of a full-featured vector drawing program. The downside of Opacity is that it lets you do things that you can't export to core graphics. At least for simpler cases, PaintCode looks like it will let you get in, draw, get your code, and get back to Xcode faster than Opacity.
After I've had some time to use it, I'll try and do a full review, including a comparison with Opacity, but my first impression is that it has a fairly basic feature set, but what it does, it seems to do very well. It has a clean interface, is fairly intuitive, and the generated code looks pretty good.
Unfortunately, there's no trial version you can download, which will likely deter some people from buying an $80 app, but in my mind, $80 is a bargain for something that can save me time in my professional life. Anyone who's ever had to figure out bezier or gradient code manually knows that PaintCode should do just that.