There are growing demands for daily gait-monitoring smart insoles which are light, soft, and comfortable both in the general population interested in sports and people with disabilities, such as children with cerebral palsy or Autistic Spectrum Disorder. Currently available technologies are basically battery-powered systems, which are bulky, heavy, and not ideal for in-home and everyday use. This study introduces RFInsole, a battery-less smart insole based on RFID (Radio Frequency Identification), tracking the sequence of foot pressures within a stance. RFInsole utilizes passive RFID tags and push button switches, so that the foot pressure can activate the tags at each location. Soft, thin, affordable, and simple structure of the device open broad possibilities to implement the same system into lighter and soft applications such as socks or pressure-sensing garments.