ARDUINO
Arduino is a small computer that you can program to read
information from the world around you and to send commands to the outside
world. All of this is possible because you can connect several devices and
components to the Arduino to do what you want. The Arduino is the best way to
get started into to the world of digital electronics.
The Arduino language is merely a set of C/C++ functions that
can be called from your code. Your sketch undergoes minor changes (e.g.
automatic generation of function prototypes) and then is passed directly to a
C/C++ compiler (avr-g++). All standard C and C++ constructs supported by
avr-g++ should work in Arduino.
ARDUINO Resources -
Using the Ultrasonic sensor HC-SR04 with Arduino
Arduino Humidity Sensor