The Karolinska Institute in Sweden tested drones to rush defibrillators to simulated heart-attack patients and found they arrived in an average of 5 minutes and 21 seconds, versus 22 minutes for an ambulance to arrive in a six mile radius.

Why this matters: The survival rate for people who go into cardiac arrest outside of a hospital is low: 8-10% in the U.S. Reducing the time that elapses before defibrillation is a key factor for increasing survival, according to the American Heart Association.

The limitations: The 18 trial runs were only performed in good weather conditions, the authors note. And when a drone lands, there may not be someone trained in defibrillator administration but bystanders talking to paramedics over the phone or through a speaker on the drone could talk them through the process.