"One way is to use standard non expensive (and perhaps far less shiny and integrated) hardware plugged some peripherals and write a quick demo for it." "Few days ago, I actually tried the concept on two "potential" customers, by using some hardware peripherals I managed to put together, and a very basic software, something which is far away in terms of design, quality and user experience from the final product, and in fact, the two customers simply didn't want to stop "playing" with the product."

You have answered your own question. A minimum viable product. Add to that a demo of how you envision the final product and how customers interact with it. Go!