Well, after doing some searching I found this:
If I am not mistaken, this will work with road runner, it plugs into the serial port, then you solder a sensor on one of the channels. right?
Now my question is, if I need to place the sensor outside the car, what is the best placement for the sensor, since I am trying to read outiside temperature. And since the sensor is so small, I am guessing it might break off easily.
Also is there a way to switch between the channels in case you want to use another sensor, let's say inside the car?