It's not a question of if it's a great idea or not, but can your idea be transformed into revenue for the company. The "build it and they will come" strategy is really based on hope. Hope that you have found a unique solution that the market will respond to.
When exploring new ideas, doing your homework is critical. From my experience, the most valuable commodity you have is your resources. It's not just the cost of time and talent from exploring the idea, but also the missed opportunity cost from having your resources tied up and unavailable for other ideas/projects that would be more cost effective.
When exploring new ideas, I have found exploring the following topics can be invaluable in making a solid informed business decision about whether to move forward and dedicate resources to the idea.
The challenge wth some of these topics is they will be based on your best guess. When performing your initial analysis, I feel it is best to review the information with a diverse team of key persons in the organization. Working with a small "tiger team" with help keep the discussions productive. Different areas of the company should be represented: business, financial, development, support, and order fulfillment, etc.
As with any great idea, the road to success is not only based on the need in the market place, but how it is executed and realized in the company. The more work done up front will make a direct impact on choosing the right area or idea to invest in your organization.