DIY Digital Tape Measure
by electronics for everyone @ instructables.com:
Today I hope to teach you all about ultrasonic sensors and hopefully by the end you’ll have a nice little digital tape measure of your own to use as you please. This is my second version of this project so if you can get it as small or just don’t feel like dealing with the Arduino Pro mini feel free to change it in any way you want.
DIY Digital Tape Measure – [Link]