Check out:
http://www.plxkiwi.com/kiwiwifi/hardware.html
I have this unit and it works pretty well.
It uses a wifi connection, not a cable.
I keep it attached to my OBDII port all the time.
There is an iPhone app to display and log the data (called REV).
I'm not that impressed with the iPhone app.
Their advanced unit + iMFD might fill your needs.