This Bluetooth adaptor from Jabra connects to a 3.5 mm jack and will transmit music wirelessly from your music player to your Bluetooth stereo headphones. I was looking for a long time for a gadget like this, and the price i think its great. You can find it at Amazon for $28.99, which i think its cheap for the product you get.

Thanks to Jabra Bluetooth stereo you can now listen to your favorite music without the hassle of wires and still stay in touch through your Bluetooth mobile phone. Simply plug the Jabra A120s adapter into your PC or music player, pair up with the Jabra BT620s Bluetooth stereo headset and – PLAY – you’re good to go! And if you’re waiting for an important call, or just want to stay in touch, you can also pair your Jabra Bluetooth stereo headset with your mobile phone at the same time.

Jabra Bluetooth Music Adaptor: [Via GeekAlerts]