Time, Countdown, and Alarm as Wallpaper

Is it possible to set time as wallpaper and also use that time-wallpaper as a countdown timer and for alarm? Any application that would do that?

If by wallpaper, do you mean a constant background that is unaffected by activity on the Desktop like conky?
A desktop widget should do it.
There is the alram-clock-applet which lives in the panel, not the wallpaper...