[Erv Plecter] likes to recreate movie props that actually work. This time around he’s making the motion detector device from the original Alien movie. You’ll immediately remember this prop after seeing and hearing it in the video after the break. For our money, the most brilliant part of that movie was the use of rhythmic sounds to boost the intensity of the tension in the viewer. [Erv's] build captures that feeling, with the steady beat of sonar and the rising pitch of a ping as an object moves towards you. The device can easily track your own movement, as it contains both a GPS module and an electronic compass. He mentions that there is a motion sensor as well, but is a bit vague about how that part of the build works. Still, it’s a nice little piece which looks great despite not being quite finished yet.