Amazon is certainly in the lead in terms of total locations. All of their locations are stores they own, however. The race right now is to show this tech working in existing stores, with a fairly light (aka scalable) install process. We have multiple installs in existing stores at the moment, running in "shadow mode" to confirm the accuracy is the system. These sites are predicting the carts of hundreds of people a day, and seeing good results.
Can you give us a sense of how many transactions standard is doing every day with it's tech that's further along / more deployed than Amazon? At least the SF location I visited had steady traffic so Amazon is collecting some real data (selection a bit limited so go grocery interesting to me)