Learn me: Driveway monitors

I am in need of a reliable yet inexpensive monitor for my driveway. I've been looking at reviews on Amazon and am still unsure which one to buy. Basically I only need to tell when cars are entering my driveway and I don't want to be alerted by squirrels, raccoons, wild turkeys or even falling leaves.

Does anybody have any first hand knowledge?

I saw that Harbor Freight sells one for $17 and I'm tempted to give that a try first.

I want one also. Let me know what you to with and how it works for you.

This one does not fit in the cheap department. But is a good unit for some applications. Its from Dakota Alert and works based on magnetic field so it only picks up vehicles. Sensitive enough to pick up my son riding his moped up the drive. Sensor is buried under drive (I tossed mine inside a culvert that runs under my gravel drive) and box is mounted on post next to it. Box outside transmits radio signal to reciver in house. Mine is about 200 ft from the transmitter. I have had it installed for about 2 years now. Still on same batteries for outdoor unit. Working good so far.

What does a driveway monitor do?

In reply to 92dxman:

If it's anything like my time as hall monitor they were a sharp looking sash and get picked on.

In reply to 7rx:

Sounds a tone like a doorbell when triggered. The one I have also has a relay output to be hooked up to home alarm system.

In reply to 7rx:

Thanks. That's gonna be hard for me to install with an asphalt driveway. I wonder how the guys that install invisible dog fences cut a groove in blacktop?

In reply to jimbob_racing:

How wide is your drive? You might be able to bury it next to the drive. I dont know the radius but the object just needs to pass near the sensor.

jimbob_racing wrote: In reply to 7rx: Thanks. That's gonna be hard for me to install with an asphalt driveway. I wonder how the guys that install invisible dog fences cut a groove in blacktop?

The website says the sensor is placed parallel to the driveway. I might have to check this out further myself.

Something like this?

In reply to Hal:

Hmm. My driveway is pretty wide but I'll look into the magnetic sensor. I was at Harbor Freight the other day and I bought their $17 sensor just for the heck of it.