Apple has applied for a patent for an interesting take on wireless charging, allowing a Smart Cover with embedded battery to recharge the iPad.
At first blush, Apple's invention, aptly titled "Integrated inductive
charging in protective cover," appears to simply be a first-party
incarnation of upcoming products that use inductive charging to transfer
power to an iOS device. These components usually incorporate an
induction coil and transformer that outputs power via a cord plugged
into the device's dock connector. Apple's patent filing describes
something different.
Instead of sourcing power from a stationary dock, Apple's invention
calls for a tablet case, or more specifically an iPad Smart Cover, to
hold the inductive power transmitter. In some embodiments, an internal
battery is disposed within the case, basically creating an "on-the-go"
wireless charger.