I have found a training aid called "The Automatic Swing Trainer" (not the tempo thing made by Dave Pelz but if you have used that please say so I'm interested in it). If you have used it please tell me who you like it. I live in Michigan so I want something to help me over the winter and if it does what it says it does it should.
http://www.automaticswingtrainer.com/
http://www.automaticswingtrainer.com/