Amazon Drop Ship Bot is an application that automates the task of shipping items from a database directly to the buyer using the cheapest supplier, which is usually Amazon.
One challenge is to fly under Amazon's radar, not letting them know that the system is a bot, which can be accomplished by limiting the amount of requests that are preformed in a given amount of time and by utilizing multiple accounts.
The biggest hurdle is that Amazon has recently added captcha challenges to the sign in page. This has been circumvented by keeping the bot's user session alive with fake requests and/or sending the captcha to a 3rd party for solving.