Now a days, you create a basic 1 page landing page on Instapage.com with a free mailchimp account to collect emails and start putting the idea out there through channels such as producthunt.com, Facebook Ads (target other countries for lower CPC), and Google AdWords targeting (with .25 cent CPC) to start getting some traffic.

In your "website test" include a contact form and a way to submit email if a person is interested. This will also help in getting other people to help you (show that, "hey, people really want to buy this.")

What you're doing is putting your website and app in the market first to see the response. You'll get an idea how much it costs to acquire a customer, or if people are willing to pay for it.

I think you can do all this yourself. With the landing page and material, make sure it is clear that you are not preselling an app you don't have but taking info for people that are interested.

You can probably find a person on Elance that can assist with feedback and making the app.