AT&T provides several relevant services under its Wireless Parental Controls umbrella. The Purchase Blocker feature prevents children from purchasing premium content, such as ringtones or games and the Content Filter restricts access to content inappropriate for younger users. Whereas these two features are free, the more comprehensive Smart Limits program is $4.99 per month per line and allows you to restrict phone use to certain hours, block unwanted incoming calls and texts, and set monthly data, text and IM messages.
For $4.99 per month per device, Verizon offers similar services. Parents can set usage limits and block calls and texts. What stands out is that you can set up "trusted contacts" who can always be contacted, regardless of any restrictions that have been set up.
T-Mobile’s Family Allowances program ($2 per month) allows you to manage the allotment of minutes, messages, and downloads on all the lines on your account, while the FamilyWhere app (available for Android) comes in useful for tracking down family members (via GPS) using their mobile phone’s location. The app itself is free, but at the service costs $9.99 per month for 10 lines.
Sprint, on the other hand, allows you to set up parental controls via My Sprint online for no extra charge. In addition to restricting Internet access to age-appropriate content, you can block undesired incoming text messages, block content purchases, restrict incoming and outgoing calls to pre-approved phone book contacts, and prohibit use of the camera.
Android Parental Control (free for Android) allows you to filter and display only allowed apps. These settings are password-protected.
Kids Place – Parental Control (free for Android) similarly restricts use to approved apps and prevents kids from downloading other apps, making calls, and other functions. For small kids, this app includes an auto app restart in case they accidentally exit the app they're using.
Kaspersky (free for iPhone, Android) offers one of the simplest safe browsers, filtering out content that is inappropriate for young users on mobile devices. It even comes with a handy set of instructions for parents, including screenshots.
K9 Web Protection Browser (Android, iPhone, iPad, iPod Touch, Windows, Mac) similarly allows you to block websites in more than 70 categories, forces SafeSearch on the most important search engines, and allows parents to view reports on web usage and more. For example, a search for "sex" using the K9 Web Protection Browser will yield zero results.
AVG Family Safety (iPhone, iPad, iPod Touch, Windows Phone, Windows, Mac) comes in useful if you want to customize profiles for different children, allowing you to limit websites and track social media activity for each. AVG even incorporates key-stroke technology to detect words that are used to victimize children online. In case such a phrase is found, you will automatically be notified by email or text message (given that you are logged in). The problem I found with this app is that if you search for a blocked term (e.g. "porn"), the AVG browser will show the results but label them as blocked. To continue browsing, you have to exit the app and restart it. Simply not showing blocked results would be a better alternative.
If you simply want to limit the amount of time your child spends on his or her phone, consider Kid Time ($0.99 for iPhone). You can set a daily time limit for each child, and the device is automatically disabled when that period is over. While the paid version allows time tracking for more than one child, the lite version is ideal for those who have just one child or just want to try the app.
If you want to limit the length of incoming and outgoing calls on an Android phone, you can configure the free Call Timer on your kid’s phone, which means the call will automatically disconnect after a set amount of time. However, this app is not designed specifically for parental control purposes – it's actually billed as a moneysaver for consumers who are charged by the minute.
To limit the apps and other content your child downloads, Apple offers a useful guide to setting up parental controls on iTunes.
In the Google Play store, Android apps are labeled "Everyone, Low Maturity, Medium Maturity or High Maturity," which you can use to set up filters. Droid Lessons shows you how.
PhoneSheriff ($49.99 for 12-month license; compatible phones listed here) offers text and call blocking, time restriction, web/app blocking, and content monitoring.
Mobile Spy (starting at $49.97 for 3 months; Android, iPhone, BlackBerry, Symbian, Windows Phone): offers similar services, as well as social media tracking and recording of text messages, photos and videos.
eBlaster Mobile ($69.95 for BlackBerry and Android) provides parents with text message transcripts, records BBM chats, email activity and keeps a voice call log.