PressPay grew out of a project to create a web store for a client. He wanted a site to sell T-Shirts but was overwhelmed by the complexity of most e-commerce plugins. He already had a blog post about the T-shirts and his readers were commenting that they wanted to buy them. He just needed a button on the blog post to complete the transaction. PressPay is that button.
Write a shortcode into any post or page and PressPay embeds a button in that page. When your readers click the button they will be prompted to enter their credit card information and are walked through the rest of the sale.
PressPay uses Stripe as a backend to process transactions so you need an account with them. You should also be sure to enable ssl on any site that you use to collect sensitive information - like credit card numbers.