A method of detecting a stimulus can include detecting an output from a radio frequency identification tag including a sensor. A smartphone-based sensing strategy can use chemiresponsive nanomaterials integrated into the circuitry of commercial Near Field Communication tags to achieve non-line-of-sight, portable, and inexpensive detection and discrimination of gas phase chemicals (e.g., ammonia, hydrogen peroxide, cyclohexanone, and water) at part-per-thousand and part-per-million concentrations.