Here is an amazing product that started as a kickstarter product. I have one and it works great, and it supports bluetooth 4 so it uses less power. It is also backward compatible if you don't have an iphone 4s or 5 (or any other device that supports bluetooth 4.
http://theauris.com/
They are pretty cool. If the phone is in your pocket, you can just turn on the auris. Once it's paired, it will automatically reconnect to the device it was last paired with. You can change it easily by holding down the mode button on the front as well.
Here is how it works:
There are three buttons:
The mode button on the front: You press and hold the mode button until the light comes on to power on the Auris. Once it's turned on, it will automatically connect to your phone if it was the last device you had it connected to. You can tap the mode button to alternate between play and pause. If it's on, you can press and hold it to turn it off. To put it in to pairing mode, when it's off, you press and hold the mode button. The led will turn on and blue. Keep holding it until it alternates between blue and red. Then it's ready to be repaired.
The "Up" button on the side: you can press and hold it to turn the volume up. If it makes another tone, it means it's up all the way. You can tap it and it will forward to the next song.
The "Down" button on the side: you can press and hold it to turn the volume down. You can tap it to rewind the song.
There's a microphone. This microphone doesn't do any noise canceling. You can use it to issue Siri commands or you can use it as a microphone while you make a phone call. With the lack of noise canceling, you might want to consider not using this in your car if the audio is going over your stereo system. However, it's still great for Siri commands. One more thing about the microphone: when you place a call or receive a call, if you want to use the handset instead of this microphone, make sure you change the audio source to the iphone instead of the Auris.
There's a battery. With the battery, it doesn't need to be plugged in to power all the time. When it's peered with an iphone, there will be an additional bar graph at the top on the iphone display, next to your iphone's battery indicator.
It has a 30pin dock connector. It uses this to charge the battery It will also send audio through that same 30pin dock connection if your stereo supports it.
It also has a 1/8" stereo jack. You can use this as a lineout or headphone jack.
There are other bluetooth to line out devices but this one is the most feature rich and really a cool little product. I highly recommend it to anyone that needs such a device. The others that I've seen are not bluetooth 4.0 compatible (requiring less power) or don't have a micrphone or don't have the controls, or don't have a battery.
Hopefully that helps!
