Apparently, 20 percent of patients who need to wear defibrillators dont actually keep them on at all times — even if they mean the difference between life and death. So, a group of biomedical engineering students from the John Hopkins University designed a new type of wearable defibrillator, which is unobtrusive and comfortable unlike traditional harness designs. The undergrads version takes on the form of a stretchable, waterproof vest fitted with sensors.