The iPhone and iPod are closed. What about the Apple TV?

Ever since the iPhone was announced, people have asked if developers could write applications for it. After all, most "smart phones" run a stripped down version of Windows that allows you to install software on them. It's only natural that Apple would allow the same feature, right?

Not necessarily.

Apple has, so far, closed development of the iPhone to 3rd party developers. Apple's official reasoning is that they want the phone's performance to be rock solid, and installing software from various sources can cause problems. Most expect Apple to open up support in the future.

This is in stark contrast to the iPod, which Apple hasn't opened to developers and shows no signs of ever doing. They've signed deals with major parters to add applications and functionality, but there's never been a software development kit that lets you write softwares specifically for the device.

Where does this leave the Apple TV? Is it a device that people want to write software for, like the iPhone? Or is it a device that most people are content to let stay closed, like the iPod?

Is there a killer app for the Apple TV that you'd like to see? Are you a developer with a great idea you'd like to implement? Will the Apple TV ever be opened to 3rd party developers?