The father of Briton Lucie Blackman killed in Japan has launched a safety service using text messages.
Tim Blackman's search for his daughter inspired Safetytext
Users create a message detailing their travel plans and set a time delay of between 30 minutes and 24 hours.
If they have not returned and cancelled the message by the deadline, it is sent to a chosen friend or relative.
Tim Blackman came up with the idea for Safetytext while searching for his daughter, who died in Japan more than three years ago.
Japanese businessman Joji Obara is currently on trial charged with killing Ms Blackman and another foreign hostess, and with raping six other women.
The Safetytext service stores photographs, contact details and the names of friends and relatives, releasing them to police in the event of the customer disappearing.
Users can register for the paid-for service at Safetytext.com. Each message costs 50p on a pay-as-you-go basis, or 33p if paid for by monthly £5 top-up.
Mr Blackman, from the Isle of Wight, told the Sunday Telegraph: "If Lucie could have sent a Safetytext, she may have been found in nine hours not nine months.
"I said 'What could have made a difference?' Lucie was here one minute and then no-one knew where she was."
And he explained the youth-orientated thinking behind the innovation to BBC London.
He said: "We were looking for something in a medium that youngsters would understand and texting has really exploded in the last three years.
"We are hoping that in time it will be used by people, such as care workers, who get themselves into situations where they would prefer a little safety back-up."
Ms Blackman, from Sevenoaks in Kent, disappeared in July 2000 and Mr Obara was arrested three months later.
The remains of the 21-year-old bar hostess were not found until February 2001, in a small cave 200 yards from a beachside apartment owned by Mr Obara.
Police with dogs had searched the area close to the cave three days after Mr Obara's arrest.
Prosecutors allege Mr Obara entombed Ms Blackman's head in concrete before burying her body in eight parts.