I have been using the Mighty Mule units for 4 years and am very satisfied with them. I have two of them installed and they trigger the same receiver in the house. The only problem I have with them is that the receiver sounds are very high frequency and as a lot of men are as they get older, they lose the ability to hear high frequencies. I fixed that by setting the receiver inside a box with a microphone to a larger speaker. These units require you to bury a sensing rod along the driveway, therefore they do not pick up anything except traffic on the driveway.
I previously had an infrared unit that was constantly giving false alarms, usually from wildlife, even birds. I used to think my current one was giving an occasional false alarm until I installed my security camera and discovered that occasionally someone would use my long circle driveway as a turnaround and be gone before I could get to where I could look outside. They are mostly people pulling horse trailers and those I do not mind. Others I am not happy about. I suspect they are just nosy. There is a big equine place about a mile north of me and I suspect a lot of those come from there where they miss the turn to get over to the major highway. In fact, that happened just recently in the late evening after dark. He pulled off to the side of the road after he missed the turn. I pulled alongside of him and asked him if he missed the turn and he said he did. So, I told him to follow me home and he could use my long circle driveway to turn around. He stopped long enough during his turnaround to thank me for the help. I pull a 31ft gooseneck dually flatbed so I can sympathize with them.
One final note. Do not buy a Mighty Mule from Northern Tool as I did my first one. They are much higher priced. Shop around for a better pricing.