I'm going to follow along with the Stanford iPhone Application Programming course which is being offered for free online though iTunes U. Also, now that OS 3.0 is released, I can get access to it without having to be a paid iPhone Developer or having to sign an NDA. I might sign up for the dev program, but it's $99 and I want to make sure I will actually use it.
So - write some apps first, follow along with the course, see what cool things I can do, use the emulator, etc. And then if I want to release something to the app store I will sign up then.
The first app I want to create is something to find/control Phidgets over the network. Since the Phidget webservice has built-in Bonjour support, this could actually be pretty slick. I'm thinking something like the Jaadu interface for automatically finding Phidgets. (Jaadu is an awesome VNC app that will find computers with screen sharing turned on).
I think a Phidgets app would be really cool and slick, though I have to admit that I'm probably in a minority, as it would only appeal to people who have both an iPhone and Phidgets. Either way, I'd like to get it on the app store and see if people grab it.