My day job is with a company I co-founded, called SonoPlot, Inc., which manufactures and sells robotic systems for the printed electronics and biological research markets. Among other things, I write our control software, which is Cocoa-based, running on Macs.
I do Mac and iPhone development on the side in my one-man company Sunset Lake Software. Lately, like everyone else, I've been doing some tinkering on the iPhone. In fact, I teach a class on the subject at the Madison Area Technical College, for which the previous semester's videos can be found on iTunes U.