Circle with Disney, now on sale for $99, is a small cube that pairs with a local Wi-Fi network to give parents control over what kind of content their kids’ devices can access, and for how long. If your youngsters are watching too much YouTube, for instance, you can limit their iPhones to an hour (or more, or less) of videos. You can “pause” Wi-Fi throughout the house for an extended period, and monitor time spent not just online but on which apps and content types.