The first one is not too difficult. The only thing is that it would require a "settings" screen to adjust the timeout.
The second one is not possible with a regular app, I think. A normal app simply cannot know when the user hasn't touched anything for some time. Android simply does not provide this information. Maybe something like that can be done at the system level, or maybe with a launcher. I don't know if launchers can do that. I'll take a look.
For the moving digital clock, I'll see how I can have one moving across the screen.