This is my first portable Arduino project, and I'm pretty proud of how it turned out!
It uses a DrinkShield and a Diavolino, and is contained in a square metal junction box with a plexiglass lid.
I had to drill and dremel the plexiglass so the sensor and LEDs could protrude through. I threaded a wire loop through the junction box and clipped a nylon strap to it, to make carrying it easier. The battery box is attached to the outside of the junction box with a velcro strip.