A pocket-sized personal trainer

Helping you learn exactly how to eat in order to lose or gain weight beyond the obvious "stop housing McRibs"/"start housing McRibs", the Breezing's a pocket-sized, breathalyzer-esque gizmo that works in unison with a smartphone to measure your metabolism over time, then generate a highly customized diet and exercise plan. When you breathe into it, data's beamed to your phone over Bluetooth, and a dedicated app tracks changes from the last measurement, checking for shifts in "resting energy expenditure" and "respiratory quotient". Then, based on your current weight and weekly fitness routine, it'll recommend a target caloric intake for the day to reach your goal ASAP.