Meet the VHOOP: an app-enabled hula-hoop that connects to your smartphone via Bluetooth to give you a fun workout. It has 8 pieces that you can put together in a minute to get started. Its mobile app lets you view the number of rotations and the length of your workouts. It also lets you know how to maximize your workout.
The device has a battery that lasts up to 15 days. It is water resistant. You can find it here.