Insulin pump. It is worn on the outside of your body. Patients can clip it on a belt, put it in their pocket, put it in their bra, and there are even underwear or clothes with pump pockets built in. It is attached to an infusion set on your ABD skin by tubing. Go check out one of the pump websites. One of the best pumps is still the Medtronic pump. Check out this website: www.medtronicdiabetes.com/compare.
On the chest. There is a harness that can be used for placing the pump on your chest. There is also an arrangement where you can hook it to a bra, or, perhaps, in a pocket.