Hey there, Zepia!
I have not seen any landing page applications however, you can reach out to an Expert to help you out! There's a list of talented folks here: http://experts.shopify.com/!
To actually create a landing page, you'll have to modify your index.liquid template in the Template Editor (Themes>Template Editor). You can remove all existing code from index.liquid and replace it with that of your own for a landing page. All formatting throughout the rest of your shop will remain, but not for index.liquid which is your shop's homepage. Please advise that you should backup your theme before attempting anything. You can simply duplicate it in your Themes section.
Happy holidays!!
Liz Bertorelli :: Shopify Guru
liz.bertorelli@shopify.com
