I think REM detection is not required if you can set up a simple time based alarm. Then I thought about Vibrating Watches. Simple. They have those.
http://ca.search.yahoo.com/search?vc=&p=vi...t&tab=&ei=UTF-8
I found a cheap one that vibrates for 20 secs and you can set the amount of time before the next repeat.
http://www.azhearing.com/cgi-bin/shopper.c...ction&key=VL300