How to Monitor Text Messages:
http://www.ehow.com/how_###-###-####_monitor-text-message...
Step 1- Get over the idea that you are spying on your child if you decide to use this program and monitor cell text messages. Yes, there is a level of respect that you need to give your child because this will foster in them responsibility and trust, however, the ultimate responsibility for safety lies in parenting. Making the decision to monitor your child's cell phone text messages might be a solution that saves them.
Step 2 - Sign up for RADAR. Copy and paste www.mymobilewatchdog.com into your browser. This program will monitor cell phone calls, text messages, instant messaging, picture messages, and email. This will enable you to be notified when your child receives any of the above, as well as have access to the content. You receive the same message as your child. Each day your child receives a message that tells them his or her content has been reported to the parent, so your child is aware of the cell phone monitoring.
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This and other programs like this costs money. If you are unable to sign up for a program like this, set up other rules for your child around the use of their cell phone, email, and computer usage. It's acceptable to have the passwords and check in on what your kids are doing. What they think is harmless information can be the perfect thing a predator needs. Make sure to have open dialogue with your family about these issues.
Also check with your cell phone provider they may offer the silimar program for parents. The only thing we are required to give our kids is food, clothing, and lodging. Everything else is a privilege we as loving parents give them.
If you put "pot smoking" in the search box on the mamapedia website you'll get a list of moms with similar problems. Good Luck!