I’ve used the following tools to get an estimate but still feel like I’m just polishing instead of verifying. So would love to hear how others have done it.
Google’s key word tool for traffic estimations and competitiveness
Software for download counts and price reference for products in the space on download.com
Alexa for traffic estimations of potential competitor sites.
Google Links for who are the movers and shakers for link juice.
The real grey area prior to a product really being put together is I then estimate a conversion rate and typically just guess using a 1% as a starting point which is completely arbitrary but gives me an idea.
So I realize there are holes in my process and would love to plug them. Suggestions?
I've seen your demo, but you need to let people download the software regardless of the status (If you don't have an installation file, create one.). Tell anyone you know with a computer to go to your site. See how many download it. How many are willing to give feedback? Will they mention it to anyone else? It may seem like an exercise in finding out who your friends are, but it will give you a lot of insight into how useful the app is.
I know because I told everyone about my site and an app to install and only one person did it. They loved it. So what does that mean? I've either got a narrow niche market or one heck of a niece.
I'm getting useful results from running a survey on my site. You can just ask people to fill it out (I've seen people do it), perhaps in return for getting the results when you're done. It's also a good idea to give something away as an incentive or run a competition (I've heard positive feedback about competitions as an incentive).
Besides that, I looked at government employment data to get a rough estimate of market size by country.