The traditional fixed point-of-sale cash register is not only expensive and bulky but also inconvenient to use. Therefore, the goal of this research is to realize a live-trading mobile cash register that can handle multiple online transactions concurrently and is capable of intelligent back-end data processing and analysis for transactions, especially applying Web technology and a back-end database for data exchange or third-party payment over the Internet. Regarding the Internet of Things, the wireless networking protocol Bluetooth is used to connect front-end devices to their smart-card-related accessories where near-field communication (NFC) technology is used to read data stored in a smart card for connection and data exchange between the smart card and the front-end devices. In this way, a point-of-sale system is not limited to being installed or fixed on a front desk; instead, it becomes a mobile cash register and accepts online payment, providing consumers with convenience and fast transactions.