The ability to measure speed and tilt is important in many robotic applications. You'll need to add an accelerometer/gyro sensor for this. This device measures the tilt using very small gyros, devices that spin and resist changes in orientation. When these changes occur, the resistance to change can be measured. The device also measures movement using an accelerometer. An accelerometer measures movement in one direction using very small (MEMS) machines that respond to motion by outputting a small signal.

Providing this information can help you know how your device is moving. Fortunately, there are chips that can provide this functionality. One of them is the MPU-6050 chip, which provides a complete set of information on movement, including the acceleration and tilt. There are several different manufacturers who place this chip on a small board accessible from Arduino.

One of these is the SparkFun version, the SparkFun SEN-11028, available at sparkfun...