A focused timer-operated water sprayer would be a great silent alarm clock. The alarm clock would push the button of an electronically operated water sprayer.
The main advantage of this solution is that it's more effective than a sound- or light-based alarm clock that you can switch of and keep sleeping. The water sprayer make the pillow wet and thus unpleasant to sleep on.
A deflated inflatable pillow can be put under the main pillow, beneath the bed sheet. Just before the wake-up time, a timed air-pump would start inflating it, thus making further sleeping uncomfortable.
PS: A similar silent alarm clock can be provided to the passangers by conductors in Japanese railroads.