The Raspberry Pi Radio Module 2 is a $4 wireless module that measures 16.5 x 14.5mm and has an Infineon CYW43439 radio for WiFi 4 & Bluetooth 5.2, an onboard 2.4 GHz antenna, an SPI host interface. https://www.raspberrypi.com/news/raspberry-pi-radio-module-2-available-now-at-4/#RaspberryPi#RaspberryPiRadioModule2