I have recently discovered the smartEverything prototyping board for Sigfox. This board was used during the SigFox maker tour and It is really nice for creating some prototypes and evaluate the technology.
The board is an Arduino board based on an Atmel SAM D21 MCU (Cortex M0) with 256KB of flash and 32K SRAM running @48Mhz
The most important part is concerning the sensors available on the card and this is clearly the best point about this board : you have a lot of them available : crypto authentication chip, BLE module, GPS, NFC, Accelerometer / gyroscope / magnetometer, Pressure / Humidity / Temperature sensor, proximity light / sensor, RGB Led, Led & push button. It can be powered by USB or external 2xAA batteries.
The board cost is about 106€ and can be found at RS. It is provided with a sigfox network access to the backend.
This post detail how to get start with the board