Dear PropellerHeads: I'm using parental control and filtering software to block inappropriate content from my children's desktop computers. How do I do the same for their phones?

A: We've found that a few well-placed pieces of duct tape works wonders when it comes to blocking offensive images on a smartphone screen. Unfortunately, it also makes it exceptionally difficult to play Angry Birds, so we've had to look for other options.

If you're looking to secure an Android device, check out MobileMinder (mobileminder.com). It supports GPS tracking, text message filtering (to foil "sexting" or "cyberbullying" attempts) and monitoring of call logs and browser history. Note that it monitors content, but does not filteror block it in the first place. It helpfully displays an icon on the phone screen as a reminder that your child's activity is being monitored and costs around $5/month.

Also for Android only is ParentalFlux (parentalflux.com), which lets you block numbers, grab a phone's contact list, view the web history, delete the phone's data or lock it remotely (in case it's stolen), and even record audio calls. The basic version is free, but a paid "Professional Plan" adds access to their Fluxbrowser, which uses a regularly updated filtering list to block all kinds of sites ("adult," "violent," "drugs," "games," "social networking," etc.).

Most of these tools require you to pay and sign up for an account, install the software on your phone, and then login to your account to monitor the phone's usage. PhoneSherrif (phonesherrif.com) works similarly. It runs on Android and iPhone/iPad devices plus older versions of Blackberry, Windows Mobile and Symbian (mostly Nokia) phones. (Note that newer Blackberry 10 and Windows Phone devices may not be compatible.) The cost is $50 per year.

Unfortunately, PhoneSherrif requires iPhone users to "jailbreak" their phone, which is a process that involves bypassing the phone's built-in access restrictions. Jailbreaking requires some tech savvy and voids your warranty, but is sometimes necessary because of the restrictions that Apple has placed on app developers.

Two other iPhone apps get around Apple's restrictions a different way. SafeEyes Mobile (internetsafety.com) works on iPhone, iPod Touch and iPad, and includes a custom browser with built-in filtering. They give you instructions for disabling Safari (the default iPhone browser) and locking down the phone settings (so your child can't install other browsers without filtering). It's a clunky solution, but avoids the requirement to jailbreak the phone. SafeEyes Mobile is available for $15 from the Apple app store.

CovenantEyes (covenanteyes.com) works similarly for iPhone, iPod Touch and iPad - use their custom browser, disable Safari, lock the phone down- but for Android it works through the phone's built-in browser (so no custom browser is required). It's free if you're already using their desktop software (prices vary) but like MobileMinder, it does not filter content, it only reports on it. The idea is that a parent (or accountability partner) can see reports of web viewing habits, thus providing an incentive to stay away from inappropriate material.

When the PropellerHeads at Data Directions aren't busy with their IT projects, they love to answer questions on business or consumer technology. Email them to questions@askthepropellerheads.com or contact us at Data Directions Inc., 8510 Bell Creek Road, Mechanicsville, VA 23116. Visit our website at www.askthepropellerheads.com.