LEGO

This is an array of 8 sensors with controlled light source, returning you values of the sensor readings. Your program can then decide if you wish to follow line with it or do something else. Perfect addition for Mindstroms NXT kit.

Multi-Sensitivity Acceleration Sensor (ACCL-Nx-v3) is a 3 axis digital acceleration sensor designed for Lego mindstorms NXT. This sensor works at 4 different sensitivity levels of gravitiy.
The sensitivity can be chosen in your program.
This sensor can be used to measure static and dynamic acceleration in different axes. You can use this on your robot as tilt sensor or to track the velocity profile.

Detect light intensity! The Light Sensor assists in helping your robot to “see.” Using the NXT Brick (sold separately), it enables your robot to distinguish between light and dark, as well as determine the light intensity in a room or the light intensity of different colors.

Your robot’s “ears!” Using the NXT Brick (sold separately), the Sound Sensor allows your LEGO® MINDSTORMS® NXT robot to hear! The Sound Sensor is able to measure noise levels in both dB (decibels) and dBA (frequencies around 3¿6 kHz where the human ear is most sensitive), as well as recognize sound patterns and identify tone differences.