Children trying to convince their parents that getting the an Apple Watch is a "matter of life and death" might gain some support for their argument. In the future, the wrist-worn wearable could detect medical emergencies, such as a heart attack. Finally, a useful purpose for all that heart rate data.Right now, the life-saving feature is just an idea. Apple filed a patent application for a feature that would allow the Apple Watch (or a similar electronic device) to detect medical emergencies. Once detected, a linked iPhone would take the proper action, whether it be notifying 911 or reaching out to a trusted contact.The filing explains how the add-on would work. Basically, an electronic device (an Apple Watch, for example) that monitors sensor data would detect what Apple calls “care events.” Such an event might be detected using the accelerometer and heart rate sensor — a sudden movement followed by an absence of heart rate, for example, might indicate a heart attack. The device would then transmit an alert about the occurrence to at least one other electronic device (an iPhone), which could then take action on the owner's behalf.To prevent the case of a false positive — say, you were doing jumping jacks and then your Apple Watch fell off your wrist — the device would simply ask for a response using voice, motion, or gesture to make sure you're okay. If you didn't respond, it would then email a family member or call emergency services.This would be an incredibly useful feature for any wearable and it could certainly help relieve anxiety for those of us with older parents or grandparents...as long as we could convince our loved ones to wear the watch in the first place.