Yet another fine piece of open source hardware for IoT.
A new Arduino board is available. It has SAMD21 Cortex-M0+ CPU which is said to provide integer performance on par with Raspi Pi Zero. Moreover, it provides an integrated Wifi, an integrated charge controller for LiPo batteries, and a crypto co-processor. See http://www.arduino.cc/en/Main/ArduinoMKR1000. The board costs about 30 Euros.