Can I successfully use a humidifier to distribute caffeine to wake someone up without the usual morning drowsiness?
It looks like at least one person/organization has thought of this and patented a delivery mechanism ("Delivery of caffeine through an inhalation route").

That said, you might be able to couple the system outline in the patent documentation with an alarm clock of sorts to trigger the release at a specified time. I'd certainly buy one if the price was right.

Edit: The inhalation part has been investigated. As far as I can tell, the business about administering caffeine to a sleeping person and then having them awaken into a fully alert (or pseudocaffeinated) state has not.