YoDude is wrong, mostly because Apple provides an SDK -only- for OS X. Sort of like Maemo/MeeGo, but restricted to a more closed platform.

And unlike Apple, the general software development toolkit is available on 3 platforms instead of one. Only thing missing is a system emulator, but this is of moderate value on a platform that isn't single-sourced (Apple) or focused on keeping the software in a VM (Android.) After that you're running on hardware anyway.