I don't think you understand what Bluetooth does. There is no way to charge using BlueTooth. It's a communication protocol.
There are wireless chargers, they all depend on setting your device on a charging mat. While there have been a few interesting demos and talks on the subject, consumer wireless, carry around, charging is still a ways in the future. Well, other than solar, and that's a slow, slow, method with current technology.
There are portable battery pack/chargers for the iPad. There are even one or two battery/case solutions. Google will turn up plenty of possibilities. I've never used or researched any of them (beyond noticing the occasional ad), so I won't try to recommend one.