seeed studio Wio Node;

Wio Node was born with most of the features as its elder brother:
An ESP8266 based open-source Wi-Fi development board
Supports Plug-n-Play Groves
Visual Configuration
OTA (Over-The-Air) Firmware Updates
RESTful APIs
IFTTT Application
Android & iOS APPs

Features
Cheaper, lighter, smaller, and simpler
Built around ESP 8266 Wifi module
Supports Plug-n-Play Groves
Visual Configuration
OTA (Over-The-Air) Firmware Updates
RESTful APIs
IFTTT Application
Android & iOS APPs

Specification
Wi-Fi Network Protocol: 802.11b/g/n
Wi-Fi Encryption Technologies: WEP/TKIP/AES
Expansion (2x Grove Connectors): UART0/I2C0/D0, Analog/I2C1/D1
Input Voltage: Battery holder: 3.0~4.2V, Micro USB: 5V
Operating Voltage: 3V3
Maximum Charge Current: 500mA
Digital I/O Pins: 4
Analog Input Pins:1
DC Current PER I/O PIN: 12mA
Flash Memory: 4MByte (W25Q32B)
Frequency of Crystal: 26MHz
Dimensions: 28mm x 28mm