"If she knew, she might be tempted to just leave it in some location," Betar said.
For Mark Frankel of the American Assn. for the Advancement of Science in Washington, that crosses a line. "If a parent gives a teenager one of these phones and tells them, 'It has the ability to track you,' it can carry the message 'We are concerned about your safety,' " said Frankel, who is director of the group's Scientific Freedom, Responsibility and Law Program.
"But it troubles me that someone would be tracked without their knowledge, outside of a criminal situation. When the child finds out about it, and there's a good chance they will, it's a betrayal. It carries the message 'I have no trust in you.' "
Frankel said that part of being a teenager "is to develop an independent personality. And part of that is privacy."
Tom Pratt has no such qualms. He told his two children about the GPS units in their mobile phones. But he said being a kid today is far more dangerous than when he grew up on Long Island in New York.
"Back when I was a kid, on a Saturday you left home when the sun came up and then came back home when it was time for dinner," he said. Now he worries about his 12- and 13-year-olds, and he pitched the GPS unit to them as a way to give them more freedom.
"We told our son, 'You don't have to call home every hour anymore,' " Pratt said.
Danielle Butler, whose road trip was interrupted with the warning about speeding, is practically an adult. But she said she hardly thinks about the phone that allows her to be tracked. "I don't mind," she said. "I have nothing to hide."
