I can fall asleep under virtually any conditions, but some people find it helpful to have a predictable droning of some sort in the background. Of the different varieties of noise, pink noise is one of the more pleasant. Pink noise is sometimes called 1/f noise because the amplitude (roughly speaking) is inversely proportional to the frequency of the noise. For various reasons, this is a much more pleasing form of noise than white noise.
I built a custom designed enclosure from laminated plywood. Inside is a commercially available pink noise generator, normally used for testing hi-fi equipment, and a small amplifier circuit and speaker with volume control. The unit is activated by a stomp switch, so just like an Apple mouse, the entire unit is the switch. You can turn it on and off just by stepping on it or mashing it with your fist, and I feel this is about the right level of interaction for something you are supposed to use right before bedtime.