Microchip RN171-I/RM481 3.7V WiFi Module

Ultra-low power for battery powered applications
Firmware configurable transmit power: 0dBm to +12dBm
Hardware interfaces: UART and SPI Slave
Supports SoftAP and infrastructure networking modes
RF pad for external antenna
User programmable GPIO & ADCs
Real-time clock for time-stamping, auto-sleep, and auto-wakeup modes
Run directly from batteries or regulated power supplies
Configuration over serial or wireless interface using simple ASCII commands
Over the air firmware upgrade
Secure Wi-Fi authentication schemes (WEP/WPA/WPA2)
Full onboard TCP/IP stack (no external drivers required)