I recently heard a story about a girl who was abducted in Kentucky. She gave the international distress sign (I never heard of it until this week), and luckily for her, a passing. motorist recognized the "TiK Tok sign" and called the police who were able to stop the car and save the girl. This is probably really applicable for children to know, and certainly I can see some domestic abuse situations where this would be applicable.
The sign is definitely good to know, but I strongly suggest you supplement this with real knowledge and experience in visiting violence upon another human being should the situation call for it. For that 3% of the time when all other options--including situational awareness--have failed. Take a holistic approach to self-defense that includes knowledge of first aid; enhanced situational awareness; plans for emergencies at home and when you are out and about; skill in weapons, both actual and improvised; knowledge of the law and implications/ramifications of being involved in a violent act; defensive measures at your home (locks/camera/security systems); and finally when all else fails, how to use your hands and skeleton as offensive weapons.