The "panic button buddy" would be a carry-able device, similar to an electronic car key, which would attract attention by emitting a loud alarm and sending GPS info to a community base and/or local authority.
Once while driving in San Francisco, I came upon a very loud angry fight where a man was yelling at a woman, and seemed to have violent intent. While I could not stop the fight, I did pull up to the incident, and get out of my car and stayed there until the woman could get in her car. Just by "bearing witness" I was able to help the other woman, because the man clearly didn't want anyone to see his behavior.
I noted in the research that women feel more secure with the presence of other women and that there is safety in numbers.