The change affects both new and existing coverage holders. It's also in effect for devices running Google's Android OS, which can be "rooted," a similar procedure to iOS' jailbreak.
However, the word "change" is somewhat misleading. The company actually has long covered jailbroken devices. What's really changed is that the company is now publicly announcing its stance.
Vincent Tseng, SquareTrade's VP of strategy said,
"We actually started covering jailbroken iPhones pretty much after it became an issue. It was the kind of thing that, once we started getting questions from customers, we made the internal decision to start covering it.
"One thing we have to keep in perspective is that the jailbreaking community is pretty small compared to the overall community, so we don't want to confuse the 99 percent of users that aren't jailbroken. We will definitely be making customers more aware of it, but it's not going to be plastered all over the help page or anything."
In other words, the company will support jailbroken or rooted devices, but they don't want to "really" advertise it, despite making the practice public. No matter, what, SquareTrade opening up about the policy is a good thing.
SquareTrade offers two-year iPhone 4S warranties for $99.99 (one-year for $59.99). Two-year smartphone warranties (they mean you Android, Windows Phone, and Symbian) run $124.99 or $69.99 for one year. Nicely, SquareTrade's warranties even cover immersion.