market entry

My idea is to modify the electromagnetic breaks on roller coasters to work on cars and trucks. My question is this: how should I test the need for this product? I know that people will say an idea "is great" when you ask them, but when actual money is involved that's when people tell you what...

There's already a great gold thread on the subject by the ice cream kid that you should check out if you haven't already - but here's another entrepreneur that shares his knowledge on the subject that you'll want watch. Enjoy & share your thoughts below. TL;DR..... Find the main pain point /...