What should you do with old tennis balls? You can always throw them away or turn them into something more. Take hearO for instance. It is a Bluetooth speaker in an upcycled tennis ball. It is portable and ready to pair to your smartphone, tablet, and other Bluetooth devices.
These speakers have a simple button that let you turn them on and off easily. Its grill pattern is developed to optimize sound projection. You can get your hands on these in November.