The Pololu Zumo 32U4 robot is a versatile tracked robot based on the Arduino-compatible ATmega32U4 MCU, and this kit contains most of the parts you need to build one—all you need to add are a pair of micro metal gearmotors and four AA batteries. This product is a kit; assembly (including soldering) is required.
https://www.pololu.com/product/1419This reflectance sensor module is designed for use with the Zumo shield for Arduino. It has six IR LED/phototransistor pairs that can be used for line following or edge detection. Each sensor provides an independent, digital I/O-measurable output.