[sixx]

Confidentiality Agreements are readily available all over the net. Get a solicitor to double check it and you should be good to go.
The people you need to eventually see most probably would be a business planner who should be able to advise on the viability of the venture based on your research and give advice of what more research is required to get a more accurate reading. Would be a good relationship to have as ideally this is the person who would draw up your business proposal in bankers language if funding was required by banks or alternative investors.

Something you could do rather cheaply and may provide a little piece of mind is secure the domains depending on the product or service before you do anything else, but it would depend on what you intend to name the product and whether it would be "obvious" in hindsight once in the market.
If for instance you have invented a new type of golf bag, then the chances of getting the "golfbag" domains are grim. If though it's something new (but obvious) like "golf cart turbo chargres" then you could straight away have the jump on any future competition. The same could be applied to a service if it's not a product you have in mind.
At the end of the day, I guess it's not a huge outlay if the idea falls over. .. and if anyone in future was to get golf cart turbo chargers to market, you could be sitting on a tidy little domain.