Investigators say the growing trend in so-called nanny spies comes after frightening stories of child neglect.
Parents say it's hard to find a stranger they can trust to come into their homes and watch their kids.
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The private investigators go undercover -- following and videotaping the nanny's every move.
In some cases what they find isn't pretty.
"We see a lot of nanny distraction where nanny is not paying attention to the children. we've seen nannies leave children outside of a store," said Tom Ruskin, CMP Group Investigations president.
Private investigators are joining what some say is a rise in so-called mommy spies -- mothers who post online photos of caretakers with questionable behavior.