Here is a cool iPhone case with a 100dB speaker and 2900mAh battery that lets you use your smartphone for longer and enjoy your favorite music anywhere. It lets you stream wirelessly via Bluetooth or WiFi. The Duo allows you to play your playlist from the cloud. It also serves as a speakerphone.
Users have the option to connect up to 64 Duo devices over WiFi. The battery is powerful enough to last for 60 hours of music. Costs under $150 at this time.