Wow - thanks for the quick reply Twin.  I just read over the other post and it has a lot of useful information. 
Just to clarify what I said earlier - I didn't mean using "reverse engineering."  It's an extremely simple product, I would do my own design based loosely on the other.  My concern was maybe more with patents.  The product I'm looking at is very specialized, and I was concered that maybe the idea was protected.  Anyway, I'm still a looonngg way from getting anything serious going.  I suppose if it comes to fruition I'll have to get legal advice - pooh.   
Here's a link to the products I was thinking about making: 
http://store.osmun.com/browse.cfm/2,60.html