Speaking of lucid dreaming, the other day I ran into some very interesting research about tACS (the dual of tDCS) being used during REM sleep to induce lucid dreaming in naive subjects with something like a 50% success rate: "Induction of self awareness in dreams through frontal low current stimulation of gamma activity", Voss et al 2014.

Unfortunately, a bunch of reading up on the topic of tACS indicates that there aren't any really tACS devices available which are both safe & cheap. (Which is too bad, because with an effect size like that it should both be easy to verify the effect and very useful if it pans out.)