OBDLink SX
This OBDII Can Bus Adapter connects to your USB port. It is a fast and very reliable way to connect to your Car.
Where to Buy
As of 2017-06 the device is available via amazon for some EUR 50
How to use it
Basically the OBDLink SX uses an USB to serial converter to connect your computer via USB to the ELM327 compatible chip that connects to your Car.
Usage on Mac OS X
After connecting the USB cable to your MAC you can check whether the device is visible. If you have macports/lsusb installed with the command
lsusb
Bus 004 Device 001: ID 0403:6015 Future Technology Devices International, Ltd Bridge(I2C/SPI/UART/FIFO)
otherwise/in any case
ioreg -p IOUSB -l -w 0
"idProduct" = 24597
...
"USB Product Name" = "OBDLink SX"
...
"USB Vendor Name" = "ScanTool.net LLC"
"idVendor" = 1027
From there http://pbxbook.com/other/mac-tty.html shows how you can test the connnection via a screen/minicom session. If the device at /dev/cu does not show up you might want to fix the situation - it will depend on the version of your Mac OS.
Working around a bug in Mac OSX El Capitan
There is a built in driver:
/System/Library/Extensions/AppleUSBFTDI.kext
which is the original Apple FTDI driver. You might want to reboot to activate it.