The present disclosure generally relates to a method and a hardware and software system for collecting data from retail point of sale. The hardware connects to a wide variety of barcode scanners and receipt printers. Collected data is transmitted to a cloud-based infrastructure backend system using a wireless internet connection built into the hardware. The collected data can be processed to extract item-level transaction information, and estimate the price and in-stock status of items in particular shops. A search engine can be provided using this data, which allows a customer to discover which nearby shop has an item of interest in stock. A targeted advertising system that complements this search service is also presented. The data can be used by retailers and manufacturers for business analysis and optimization.