The charm on the invisaWear has a hidden button on the backside. If you push the button two times, it immediately texts up to five loved ones to let them know that you need help with a link to your GPS location. It works with a free app that you install on your phone which allows you to enable a free and optional contact 9-1-1 feature (U.S. Only), which can share your location with 9-1-1 dispatchers during an emergency. You can also set your phone to play an alarm to deter the attacker or attract other people nearby. No charging necessary! The battery life is guaranteed to last one year but typically lasts close to two years depending on the usage. The app will automatically detect once the battery is low, and sends a notification to purchase a discounted replacement charm. The best part, there are NO annoying monthly fees or subscriptions! Our 30-day satisfaction guarantee ensures you'll love it, or your money back.