Essentially OpenDNS sits at router level not on the device; therefore it works accross any device that our kids are using such as mobiles, smart TV's, tablets, Xboxes, PS3's and laptops. Some of which often get overlooked when it comes to internet safety and all of them present the same risks, some more-so.
One feature that I particularly like about OpenDNS is that when your kids try to access inappropriate content, they are faced with a page that can be custom designed by you telling them why there access has been restricted. This can include text and a pictures.
Better still it gives them an option to email you directly from the block page and plead their case for reversing the block and allowing the site, should you wish to enable that feature.