Amazon is building a point-of-sale system based on the Kindle Fire that it will offer to merchants, according to a new report. The Wall Street Journal reports that the Kindle checkout system, which could be available as early as this summer, will let brick-and-mortar retailers ring up customers purchases using a Kindle in conjunction with a credit-card reader. As the Journal notes, Amazons entry into the world of physical retail would give it a chance to mine data on the shopping habits of customers in stores, where 90 percent of business still takes place. Thats why Amazon plans start by offering the system to smaller retailers, according to the Journal, which says Amazon might still abandon the project. In an effort to win their business, Amazon has considered offering help with website development, data analysis, and promotions, the report said.