I need to validate my idea for a webapp and show traction. Unfortunately its too complex to prototype on my own. Would a video explainer and demonstration be enough? I am thinking of creating a landing page with a video explaining the basic problem and solution. There I can use a "Sign Up NOW" call to action to seek conversions. This way I can gain metrics on whether or not it's being validated. What do you think?
-- Prototype --
I would add that you can create prototypes more simply by just using static images and adding interactive elements to them. I recently discovered MarvelApp (https://marvelapp.com) and you can create mobile + web prototypes for free with them. I would recommend hiring a designer to make the prototype look impressive if you have the funds.
-- Messaging --
On your site you want to be clear about the problem you are solving or the benefit you are providing to make people's lives better. Answer the question - Who can't live without your product?
If you have a target audience in mind, provide examples of how your product would integrate into their daily life. Provide examples and try to be as concrete as possible.
If there are other big names doing something similar to you - mention how you are different and superior so they can frame your product in their minds.
-- Traffic --
I think Andrés' ideas on getting traffic to your site are great. I would add Google Adwords or Bing Ads to the list if you have some cash to play with. In addition to bringing more traffic, this is a great way to test out which wording resonates with users the most so that you can use it on your site. Online Ads also let you play with targeting different demographics to see where you get the most interest from.