check your competitors. If you find competitors in your area this is an indication that there is demand for your product.
Making surveys, on the other hand, is not easy. You can do it for yourself, make polls among your customers by e-mail or you can make customer satisfaction surveys. However if you want to get a survey on your market segment (which can be very useful indeed) the best is to ask some survey and evaluation company for help, who are monitoring the market movements and turnovers for certain segments. Such services can be quite pricy.