
From their website:
Why can’t I use my child’s existing phone with My Mobile Watchdog? Purchasing a My Mobile Watchdog phone is the leading solution for real-time monitoring and keeping your child safe. A special phone is required. In many cases we can get you a My Mobile Watchdog enabled phone at little to no cost. Call (800) 341-8385 today to find out if you qualify.
Can I keep my existing phone service? My Mobile Watchdog works on most US and Canadian carriers. Most people won't need to switch phone service. What if I'm not happy with My Mobile Watchdog? My Mobile Watchdog comes with a 30-day satisfaction guarantee. You can cancel anytime within the first 30 days for a full refund of the setup and monthly service fees. How much does it cost? My Mobile Watchdog costs $9.95 per month with an initial setup fee of $25. Proverbs 22:6 "Train up a child in the way he should go; even when he is old he will not depart from it."