We have seen plenty of companies sell wearable devices for emergency situations. Want to build your own WiFi-enabled emergency button? jeanotP1314 has you covered. His project shows how you can build your own emergency button that sends an e-mail when pressed.
The developer used an ESP8266 WiFi Module, LED, battery, and a few other parts to put this project together. To program your device you are going to need a FTDI basic board or Arduino board. More information is available here.