NFC (Near Field Communication) is a reliable technology, perfectly suitable for pedestrian environments.
An NFC tag is a passive device (i.e. it operates without a power supply of its own) and consists of two elements, an antenna and a chip.
The antenna is used as the power supply and to transmit the information contained in the chip.
The magnetic field (13.56 MHz) induced by a reader such as a smartphone placed in the vicinity of the tag, is received by the antenna which further creates an electric current that powers the chip. The chip activates and starts the communication with the reader, which can download the stored data (with a transmission speed of up to 848kbit/s).