Startup Idea: Employee Location and Safety Tracker for Entertainment Business

Startup idea to develop a discrete, portable tracking software for an entertainment company. The system should allow managers to pinpoint employees' locations, ensure their safety, and inform them when to move to their next assignment. An additional feature could be a response mechanism for employees.

I am running an entertainment business in which my employees are sent all over the Chicago area to host grand openings, or special nights at bars, clubs, and conventions. I have yet to find a tracking device that is small enough for the employees to carry discretely that will allow me to know when they have left one event for another.
What we are looking for will combine an aspect of safety since most events are at night and many of our employees are women. We are looking for a software that will allow the manager on duty to "ping" the employee and find out their current location and be able to send them a signal or message to:

1. Verify the employees safety. 2 Verify the location of the employee.
2. Allow the manager to send a notification that their time at that event is about to expire, and they should begin getting ready to come back into the office or make their way to the next event.

While not necessary it would also BE EXTREMELY helpful for the employee to be able to hit a button to respond to the effect that they have received the message, or that there is a problem with safety or scheduling. The software for this would allow a link up to Windows, or an android phone.