Have you had a chance to look at the outdoor motion sensor FAQ yet? Although the posts are older, the technology has not changed. For example, it does discuss the options for driveway monitoring.
If you want to start with a shorter thread that might be specific to the sensor you currently have, see the following:
I’m guessing by the smartapp that you said is no longer available is that you are referring to Mike Maxwell’s zone manager? That’s no longer needed because you can do exactly the same thing with webcore.