The Nyko Wii Charge Station is a rechargeable-battery solution for Wii Remotes. It includes battery packs, covers, and the charger for two Remotes.
This charging kit is an absolute godsend. My Wii Remotes tend to have a much shorter battery life than other wireless controllers, probably thanks to the fact that Bluetooth is a big battery drain. With this kit, I can simply leave my Remotes sitting in the charger whenever I'm not playing, making sure that they're always charged when I'm playing.
This kit also includes custom covers for the battery port, which allows the battery pack to recharge. These custom covers are rubberized, making the controller much easier to grip. There is really no downside that I can see to this kit, and you'll never have to change your Wii Remote batteries again.