How small can the Arduino Leonardo get? well, it can get really small.
Nova is a new generation of Leonardo packaging in tiny form factor but still with powerful functionality.
Nova is the smallest Leonardo controller out there. It is only 21.5mm long and 20mm wide making it fit into small spaces.
When you thought some functionality had to go, a Triple Axis Accelerometer is integrated into this controller. And you can directly read the data of this sensor through IIC communication. Nova also have 10 digital I/O, 6 analog I/O and 4 PWM I/O. To make full use of Leonardo's commuincation power, it is equipped with an independent IIC, UART serial and micro USB interfaces.
A mini expansion shield with special digital cable allows you to connect normal sized sensors. You can find min 3P I/O interface and micro usb on the kit. Program and use it like the standard Arduino Leonardo.
To make the Nova a wearable controller, you should integrate a mini lipo battery management system which can be charged with micro USB.
If you think the Arduino Atmega328 Lilypad is old news then try the new ATmega32u4 Nova.
Specification of microcontroller
Notice: The battery is not included in the kit.