This is soo outdate gadget but I still love it. My cell (of the past 2+ years) that allow me to listen to music (radio, and 1 gigabit of stored music) and receive calls when I am needed so I don't get in trouble because, I sneak out working out.
As for workout thing outside of the gym provide, the ab-roller device thing. I am sure you seen guys / girls bring in into the gym. It's basically a tire with handles on each side and costs under $10 but does wonder for shoulder and ab muscle.
Recently, I've bought a forearm contraption (just a handle with rope and metal rod at the end to put weights on at the other end). It does amazing work on the forearm and when I am done, my forearm is pumped and hard as a rock. Additionally, while using it, I tend to flex the bicept and shoulder and becauase of the form, my arms look huge + pumped.