It actually doesn't need to be activated on a computer anymore. iOS 5+ allows the user to activate and start using their device without ever connecting it to a computer, and updates are also over the air.
I started developing in mid-April and released on July 1st. Most of the development was completed in about two weeks of evenings/weekend spare time; the rest of the time was spent tweaking and fiddling with graphics and sounds.
To motivate myself to complete it, I created the app record in iTunes Connect before I started working on the project. This gave me 90 days before Apple would take the name away. I plan on using this trick in the future when working on small apps.