In addition to what others have advised, here are my comments:

- Just think if you want to use your product? If not, be a customer of your own product and sell the idea to yourself.
- Make a list of a few influencers whom you know, who are in the same industry. They may not be your target customers but they can certainly understand your product idea. Write them an email for their comments and review; it always helps. I have often done that it works!
- If you have been sharing your insights (not the product idea) at some blogs, events, or communities, recall all the pain points and expectations from the audience and see how these map with your product idea.

I can share more details over a call, if it interests you!

Cheers
- Vinish