Reddit mentions of SKLZ Slice Eliminator - Swing Path Trainer

You're getting so far outside the ball, that's the cause of your inconsistencies. That's why sometimes you hit the ball straight left (when the face is square to the club path,) sometimes to hook it (when the face is closed to the path,) sometimes you hit a slice (when the face is open to the path,) and many other mistakes. You gotta get your swing coming from the inside to eliminate some common misses.

http://www.amazon.com/SKLZ-Slice-Eliminator-Swing-Trainer/dp/B00S4JC822/ref=sr_1_4?s=sporting-goods&ie=UTF8&qid=1464887042&sr=1-4&keywords=inside+approach

this thing is way overpriced, but maybe you're rich, or you can make your own. It'll get you going in the right direction.