I've had some fun with connections recently. I replaced the Head unit in my car.
There are 3 methods to connect Phones to stereos; Via AV lead for standard stereo connection with out only and no control. Via USB to provide limited control and stereo connection, control varies from device to device greatly and most are only fully conpatable with iOS. And lastly Bluetooth again varing from device to device.
However with the Jellybean update the Mass storeage option has been removed from Android. This has created a number of issues as nearly all USB connection options will no longer work! (well done Google
Hats off to the guy in Halfords, who was very helpfull while we systematically tried USB connections on all headunits on display...None of which would connect correctly to the phone. We then proceeded to try all the Bluetooth units, Again there were lots of issues and most are only compatible with iOS. Finally one connected, a Kenwood I believe...but the so called Red illumination Glowed Pink!... No Way
Down to desperation I noted that on the website they had another Sony model which was not on display...The store guy offered to install the unit in to my car for testing, so off we went.
Success!, Everything worked. being the lastest model it had the latest bluetooth standards and specifically compatible with Android phones. The Sony MEXBT3900U:- Halfords | Sony MEXBT3900U CD/MP3 Player
Bluetooth connection is excellent and easy. one setup it automatically connects without touching anything when i'm near my car. Phone numbers can be stored on the headunit and dialled. It announces when you get a text and can read then to you. Call sound quality is excellent and even though there is only a small hiden mic on the headunit I've had no complaints as it seem to pick up really well. music wise sound is good (just have to balance sound on phone as phone on full will cause distorsion went sent to headunit, mid way works) volume goes very loud. full control of tracks via unit and remote. Stream music whilst using sat Nav which then switchs to announcements at junctions.
Just about everything you could want and expect.
Only critisism would be Sonys App remote software (https://play.google.com/store/apps/details?id=com.sony.evc.app.launcher&feature=searc h_result#?t=W10
.), I can't seem to get it to work correctly on the phone, but the HTC Ones built in Car mode app is excellent and connects great.