I was thinking of something like this. I found it on ebay. Its cheap, only $15.
View attachment 7414
This Bluetooth FM transmitter is a perfect solution for those who don't have an auxiliary jack in their car and don't have Bluetooth capabilities, and it also can be used as a charger for all of your devices.
*Support A2DP, AVRCP, HFP.
*Wirelessly transmit phone call from Bluetooth mobile phone to the car FM stereo system.
*Switch to hands free model automatically from music playing status when receiving call.
*With A2DP function, stream music from Bluetooth device to car's FM stereo system.
*Supports music playing from USB disk.
*Supports MP3/WMA format files.
*Draws power from the cigarette socket in the car.
*Dual USB outputs 5V/3.4A, charges iPhone, iPad, iPod and other devices.
*Full 206 channels optional from 87.5-108MHz.
*LED display the number.
*With voltage dection to remind your car battery health status.
*Incoming call number announcement.
*Redial the last call.
Specifications:
*Color: As pictures show
*Bluetooth version: JL 2.1
*USB output: 5V/3.4A
*Transmit distance: about 5m
*Microphone effective range: about 0.5-2m
*Product input:12-24V
*Music format:MP3 WMA
*Working current:40mA
*Standby current:40mA
*Screen specifications: blue LED digital display
*Diameter: about 34mm
*Length: about 78.4mm
Warm tip: The frequency range of our wireless Bluetooth FM transmitter is 87.5-108MHZ, so you can tune to the exact station on your radio and there's no necessary to worry about the frequency or static.
Package including:
1 * Bluetooth FM Transmitter
How to operate:
*Plug the FM transmitter into your vehicle's cigarette lighter.
*Tune your radio to an unused FM frequency, then match this kit to the same frequency.
*Activate your phone's Bluetooth function, then search new device. When the phone detects a unit named "C26S", please press it to connect.
*This device is equipped with memory function, once connecting successfully, you do not need to connect again. [/QUOT
I have a Bluetooth system that is hard wired thru the fm anti. It work well however my wife has this one you describe in her 500 SL that works much better. What seems to be better is it instantly pairs every time. The hard side system does not always pair. I would go with the above or spend the big buck and install the Kenwood Apple. I have found the Kenwood Apple installed for $1000.