I’d say for $20 its worth trying. Otherwise, they just said the tape works as a cue and I’d doubt the sales pitch unless they have published some EEG studies on it.
The one I have tried and experienced some success with is http://www.hemi-sync.com/default.asp . It works on the principals of binaural beats where a different frequency is played in each ear behind some voice cueing, and ‘brain waves’ are supposed to tune to the difference of the frequencies bringing you to the slower recuperative states.
I was practicing meditation at the time and I don’t know how much of it was due to the tapes or my progression in my meditation experiments. There is adequate research showing the subsequent brain waves states obtained by experienced practioners meditating.
I ordered some home eeg boards about a month ago I haven’t hooked up yet, http://openeeg.sourceforge.net/doc/ , with the intent of playing around with some of this stuff. I also have a paper where they show how a heart rate monitor, instead of the eeg, can be used to detect rem sleep. At the end of the day, I would rather fall put a heart rate monitor around my chest than electrodes on my scalp to chart how much useful rest I’m getting.
If you give it a shot and $20 is a good price point for this, please post your results, but I think you could obtain the same result by getting in the habit of laying down in the dark with some relaxing, quiet music on, and intentionally trying to breathe real slow.