The Wall Street Journal reports that Amazon is looking at getting into the mobile POS business, by possibly providing brick-and-mortar retailers with in-store checkout systems based on Kindle tablets. 

Details are sketchy and few, but the report points to the fact that the online giant recently hired some key engineers away from mobile checkout firm GoPago, as well as some key acquisitions made in the past year.

(Read a couple of earlier reports about the Amazon-GoPage deal here and here.)

Amazon would likely go after smaller retailers first, the report hinted, putting the oinline giant in competition with existing payments players such as Square and PayPal.

"The game of mobile payments is going to be won or lost at the physical checkout, that's where nearly all of commerce is done today," said Richard Crone, chief executive of Crone Consulting, a payments advisory firm.

To draw in merchants, Amazon has considered allowing them to offer promotions or discounts through Amazon.com or its Amazon Local daily deals offers, the people briefed on the company's plans said.

But one very big question remains unanswered: whether merchants large or small are willing to enter into a data-sharing partnership with what is ostensibly their biggest competitor.

Read more about mobile POS.