Online helpline

Jeremy Parkes and Matt Westgate have developed a website www.findamobile.com in conjunction with the Home Office, the police and Crimestoppers.

The site allows registered users to search for another mobile phone user anywhere in the UK and find the precise location of their phone. The system is accurate to within 100 metres.

Mr Westgate said: "One woman bought it. She was from Gravesend, Kent, and her son used to commute to London.

"When the first wave of attacks happened, the phone lines jammed, but she used findamobile.com and found he was nowhere near that area, and had peace of mind. For us, that is very good."

Mr Parkes said they already had more than 5,000 users around the country, including parents, who needed to know where their children were, and private companies, who used it to keep track of staff.

He said users could register online and their account could store five mobile phone numbers. For security reasons, each number had to agree to be part of the account by text message. Users buy a number of searches and can access the site either on the web or by sending a text message.

Mr Parkes added that mobile phone users were told if they were being looked for by text.

He said parents could also set up areas which their children were allowed to be in, like the roads near the school, and a text message would be sent out if the youngsters left that zone.