Personal alarm

Recently fitted an alarm system to the existing cameras at my home. My elderly disabled mother has moved in, and often falls over and gets stuck. I think it would be a fantastic idea, if a personal alarm was produced to work with the alarm base station, that would send an alarm message to a couple of pre-determined phone numbers. Much the same as alerts from intrusions etc.
Something with just one button, that could be worn around the neck or wrist, that could be pressed by the wearer in the event of an incident.