We just released Stair Dismount 2 PC development preview build for Windows. It is basically a limited version of the iPhone version, which is clearly notable from the window size and UI design. Final version of SD2 will naturally have revised UI and window size. Also level creation instructions are included, which is the main reason why this early build is now available. This thread has the relevant links and instructions.
Update Jan 2011: The relevant Secret Exit forums have been closed and the PC preview build isn’t available anymore. There’s no official word about state of the possible PC version.