The Breezing Metabolism Tracker ($349) claims its eponymous device is the "world's only mobile metabolism tracker". After an overnight fast, you breath into the gadget and minutes later it calculates your resting metabolism based upon your age, weight, and height. Paired with a smartphone (via bluetooth) it can track changes in your metabolism and give you guidelines for exercise and caloric intake. Keep in mind that the company sells Android and Apple specific models; so be sure to pick the one that is right for your phone. It can help explain why you're having such difficulty losing weight. You see, your metabolism may not be "normal". If you're basing your caloric intake on "normal" for instance 1500 calories, but you actually have a lower metabolism, you're just not going to lose weight. It is a blunt tool, however. It pulls no punches and can make it seem like your goals, any goals for that matter, are unrealistic. In my case I found the device a motivator, but a tough one.
The BodiMetrics Performance Monitor ($249) is a gadget smaller than a deck of playing cards that can measure your heart activity, oxygen levels, temperature and even systolic blood pressure. Stick it in your pocket and it also functions as a pedometer. Pull it out when you're in a quiet place and it can even help you relax using biofeedback.