Parents live every day with the fear that something could happen to their children — and a multibillion-dollar security industry has grown to give them ways to keep their nightmares in check. From baby monitoring to computer spyware to home drug tests, worried moms and dads now have many, many ways to check up on their kids at any time of the day or night. Here, a look at the protective parent market, by the numbers:

Cost of a home kit to test for a single drug; kits that test for 10 substances sell for $19.95

Price of a basic baby monitor

Price of a high-end baby monitor with audio and video

Approximate price of a GPS tracker that doubles as a digital children's watch, sold by BrickHouse Security

Number of "hyper-texters" — teens who send more than 120 text messages per day — who have had sex for every non-hyper-texting teen who is sexually active

Percentage of high school students who qualified as hyper-texters in a recent Cleveland study

Monthly fee for SafeText, a system that lets parents monitor their children's text messaging

$100 to $150
Range of prices, per year, for systems such as Mobile Spy and MobiStealth, which can monitor smartphones using Google's Android operating system

Percentage of parents who monitor their kids' activity online

Price of Spector PRO and eBlaster software for monitoring online chats, instant messages, and emails

Percentage of teens who use privacy settings to hide some of their online activities from their parents or friends

Percentage of teens who say they accept all social-networking friend requests they receive from people they don't know

Sources: Associated Press, Better ParentingTIMETRUSTe