Portable bluetooth audio receiver.
With this device you can convert any type of headset to wireless headphones.
No more annoying cables while using your cell phone.

To build it, few extra components are needed:
-1 bluetooth audio module of this type: http://www.dx.com/p/universak-usb-bluetooth-v2-1-edr-receiver-w-a2dp-hands-free-black-272072
-3 AAA battery
-4 3mm leds http://www.dx.com/p/wlxy-wl-385-3mm-color-light-emitting-diode-set-white-red-blue-yellow-orange-green-307768
-2 screws for plastic diameter 3mm
-1 "Sheet Leaf Tab" for the battery holder contacts (see the pic)
-1 elastic cord 3mm x 10cm
-Some wires
-1 slide switch: http://www.dx.com/p/3-pin-slide-switch-diy-parts-black-silver-20-piece-pack-134100