I've got this one:
http://www.hobbyking.com/hobbyking/store/__55238__Quanum_Q_2D_Brushless_GoPro_3_Gimbal_suitable_for_Nova_Phantom_QR_X350_and_others_.htmlWorks really well.
It's a long way from waterproof though
I think the future is in software gimballing, stick some gyros and accelerometer chips inside the gopro and do it all electronically. Way easier than mucking around with balancing, anti vibration mounts, flexible wire and separate power supplies.
