It's estimated that some 230,000 tennis balls get tossed each year after the four Grand Slam tournaments. Now London-based design company Rogue Projects hopes to turn those used balls into functioning and highly portable wireless speakers, with a Kickstarter campaign currently in full swing.

The company's "hearO" speakers currently use tennis balls collected from the All England Tennis Club at Wimbledon. Rogue Projects is now in talks to collect balls from each of the four major tennis tournaments (Wimbledon, US, French and Australian Open).

The balls house a 3-watt, Bluetooth 4.0 speaker inserted through a hole cut out of the top, with a protective plastic grill in a Fibonacci spiral that is claimed to optimize sound projection. A charging cradle is available with a 360-degree magnetic connection, with a full charge lasting up to 5 hours (or 2-3 hours at full volume).

Acting as a protective skin for the speaker, the ball's interior rubber reportedly helps absorb excess vibration and improve sound clarity. A button on the bottom of the speaker ball turns it on and off, and pairs it wirelessly with a BT-enabled smart phone, tablet or computer.

Kickstarter pledge levels for a single tennis ball speaker start at £45 (US$60). There's also a limited pledge level of a customized speaker ball signed by 1987 Wimbledon champion Pat Cash, and costs £195 ($200). Besides standard fluorescent yellow, the balls come in six other colors. If all goes to plan, delivery is estimated to start in November.

You can see the crowdfunding pitch video below.

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