On Tuesday, Apple unceremoniously dropped a new iPhone 12 accessory, the MagSafe Battery Pack. It's a battery pack that magnetically attaches to the back of an iPhone 12 and charges it wirelessly.

But what Apple didn't say — or at least didn't emphasize enough — is that this new accessory unlocks a previously unannounced iPhone 12 feature: reverse wireless charging.

This means that, when the MagSafe Battery Pack is attached to an iPhone, and the iPhone is charging via a Lightning cable, the iPhone is actually delivering power to the battery pack.

This was noticed by MacRumors, but Apple actually confirms it in a support document.

"If both your iPhone and MagSafe Battery Pack need to be charged, you can charge them at the same time. Attach your MagSafe Battery Pack to your iPhone and then plug the MagSafe Battery Pack into a power adapter. (...) You can also charge both if you attach your MagSafe Battery Pack to your iPhone, then plug your iPhone into a power source. You might want to charge this way if you need to connect your iPhone to another device while charging, like if you're using wired CarPlay or transferring photos to a Mac," the document says.

This is interesting, because it means the iPhone 12 should be able to charge other devices as well, such as AirPods. Then again, perhaps it can only work when the iPhone 12 is plugged in.

In any case, there's no official word about this feature working with any other accessory besides the new MagSafe Battery Pack, but this may change in the future.