USA Today recommends eAlarm [-_-]

10 helpful gadgets every runner needs in the winter (Photo: Amazon)

"​Amp up your safety with an emergency alarm"

"​OK, so no one wants to imagine worst case scenarios. But when you’re a winter runner, they can happen no matter how well prepared you are. If you find yourself in an unsafe situation, this little alarm can be a lifesaver—literally. It packs a surprising punch as the world’s smallest alarm, and it’s a carabiner, so you can clip it on and get moving."

Credit: https://www.usatoday.com/story/tech/reviewedcom/2017/12/28/10-helpful-gadgets-every-runner-needs-in-the-winter/108977314/