Coach:
I don't have the time and am far from a crafty guy when it comes to training tools, so I finally caved and bought some of the swing trainers. I have to say I've been satisfied with their products and vision. I bought the weighted orb and pin, respectively.
If you're the crafty type and can make weighted tools that simulate appropriate swing paths for less money, I'd say go your way. Otherwise, let the guys at Eileen's do the job for you.
The biggest keys when allowing customers or students to use those tools is the managing appropriate grip pressure, while maintaining balance and leverage. Therefore, I'm a big proponent of the products.