EL wire, or electroluminescent wire, is a flexible wire coated in phosphor. Apply the appropriate voltage and it lights up! It looks a lot like a thin flexible neon tube. They come in many bright colors (check below for other colors) and can be driven pretty easily with an inverter.
This particular wire glows red and is 3m (almost 10 feet) in length, 2.3mm in diameter and is terminated with a JST PH connector.