tanacetum-vulgare:

Isabel Chen, a medical student at UBC, is part of a team that has invented a mobile panic button for street-based sex trade workers in Vancouver’s Downtown Eastside.

A voice or text message is first recorded onto a SIM card, which is inserted into a GPS-enabled device such as a pager that would only need to be charged once a week. Pressing a button on the pager activates the GPS and sends an emergency message and GPS location to a contact who can get help. Because the GPS is not activated until the device is activated, the anonymity of the user is preserved.

(via UBC med student develops panic button for sex trade workers | The Ubyssey, UBC’s official student newspaper)

This is such a great idea I’m surprised it wasn’t already invented years ago!