Another interesting topic would be the effect of body temperature on sleep latency and/or quality (or possibly temperature of selected body parts--there is some buzz about the so-called "cooling cap" for insomnia lately, for example).

To me it seems a big breakthrough for being able to trim sleep time down substantially would be some technology that allowed a person to pass through the lighter stages of NREM sleep more quickly so that you could spend the majority of sleep time in slow wave.