The CTA at the end is to sign up for a launch email so I guess it's not ready yet.
You're too fast, the release date for the iOS app is 16th december.
Ah. I see. Got a little confused because the Mac app is already available, so I thought it was just a matter of old sign up form not removed from site yet.
Duet is still waiting in line for approval in the app store. Launch is later this week.