I am so thankful for the existence of the iPhone. Twenty years ago, if you'd told me I'd be holding a pocket-sized computer that had a high-resolution touchscreen, a wireless always-on connection to the Internet, and a library of Hollywood movies, I wouldn't have believed it. The fact that it can make phone calls is nice too, but I frankly don't care too much about that feature. All those idiots who keep asking "Why would anyone spend $500 on a phone?!?" are really missing the point.
(See The iPhone is a piece of shit, and so is your face for an alternative opinion.)
Writing little apps for the iPhone is the only thing keeping me from giving up on software completely. (Well, OK, I guess the mortgage has something to do with that also.) At work, I'm starting my third year of maintaining a horrible soul-crushing legacy application, and it's hard for me to maintain the appropriate level of Give-a-Shit. Playing with the iPhone SDK helps.
I'm working on an application now that I hope to put in the App Store in a few weeks. No, it's not my to-do list app. I'd rather not write about it yet, because it is the kind of thing someone else could create during an uninterrupted weekend, but once it's done, I'll start the marketing.
My first app, JacksOrBetter, has not been wildly successful. I've sold about 200 copies worldwide. That's not surprising, as it's a simple game, and there are a few dozen other casino-style card games available in the App Store, many of which are free. I didn't expect to make money with that game; I just wanted to go through the process of developing something and putting it up for sale.
I doubt my next app will bring in a windfall either, but that's fine with me. I'm having fun, and people are using software I've written. That's why I got into this business in the first place.