Why does your idea need to be developed? The world's done just fine without it up until now—why now? What is the agency and the American tax payer going to get out of it? Each agency has a role to play in serving/protecting America—does your idea fit the agency’s mission?
Yes, SBIR/STTR funding is available to help your business get off the ground or develop a new product line for your company, BUT your focus needs to be on solving the need dictated by the funding agency. They are your “customer” for this money.
If the agency releases detailed topics in its solicitation, then the topic you choose IS the problem you must solve–remember, your proposal must address ALL the points in that topic when developing your solution. If the agency releases general topics in its solicitation, then you must come up with a problem AND a solution which will fit within that topic. Your proposals are not product brochures or journal articles where you are describing what you have already done; they are opportunities for you to solve a problem the agency has identified. Before you start trying to describe your solution, you MUST define the problem.