This unit was ridiculously overpriced for what it is, just a simple gravity switch with an associated wi-fi connected monitor. I was able to apply some discounts and got the price reduced but still it was in my opinion out of line on the price. My partner and I have two dogs, and we regularly go in and out with them through the garage door, as we rarely use our "front door." On more than one occasion, we got up the next morning only to discover that we had failed to close the garage door and it had been left open all night. Which not only exposed garage items to possible theft, but also allows access to our residence. Even though I did not like being screwed over for the price, the bottom line is I needed such a product and it was the only one I found which would do what I wanted it to do, i.e., essentially just tell me if the garage door is open or closed. Installation was simple, quick, and easy, and no complaints about the functionality. It shows a green light when the door is closed, and a red light when the door is open. Simple and effective. Although I'm still not happy about the exorbitant price I was charged, I have no argument about its functionality. It works.I'm really pleased with this purchase. I live on a very busy street and over a couple of decades I've lost an expensive bicycle, a drill set, and a heat gun due to accidentally leaving the garage door open.I just installed the Chamberlain Monitor so I can't comment on longevity, but I was concerned about the many reviewers who have reported bad installation experiences.After installing mine, I suspect that one of the most common causes of problems is poor placement.Attach the sensor to the garage door at the highest possible point where the sensor is still in a vertical position. That way, the garage door will have to be completely (or very nearly completely) closed before the sensor will be vertical. (Otherwise, the garage door could be partially open and the sensor would still be horizontal and register "closed.") Also, in this position the sensor will be as high as possible for ideal reception by the receiver.Place the sensor on the garage door as close as possible to whatever direction the receiver is going to be in. That is, minimize the distance between the sensor and the receiver as much as possible.But also be careful to position the sensor so that there are no metal or other super hard materials in the line of sight between the sensor and the receiver. Be particularly careful to consider the metal rails and rollers at the edge of the garage door - metal will obstruct the signal.The sensor operates on a round lithium 2032 battery but the receiver must be plugged into an AC outlet - it comes with a transformer and a 5' cord.Place the receiver in your house as high as possible and in a position that is likely to have the most unobstructed line of sight between the sensor and the receiver. A 9" relatively stiff wire antenna is attached to the receiver. It comes coiled - stretch it out carefully, removing any kinks so it will be as long and as straight as possible. Position the antenna so it extends straight up from the receiver.My receiver is positioned on a wall in the kitchen about 7' high and about 35' from the sensor. There is a workout room and a clothes washer/drier between the garage and the kitchen so I was careful to position both the sensor and the receiver so the signal wouldn't be obstructed by heavy stuff. One of my walls used to be the stone exterior of the house so I couldn't get around that - but the signal seems to be making it through just fine anyway.I first taped both the sensor and the receiver in position so I could test the setup a few times before permanently installing them.One final note: A small piece of Velcro comes with the sensor for attaching it to the garage door. I'm not convinced that this is going to be a permanent solution since we often have 100+ degree days in our town and the Velcro adhesive may not last long. If it doesn't, I may just reattach it with a dot of super glue to the adhesive side of both pieces of velco - we'll see.That's it - hope this helps.First, the good:This product works as advertised, it installs basically instantly, and does exactly what it is supposed to do without any need for configuration. Attach the smaller transmitter unit to your garage door (after inserting the included button-cell battery), plug the base station into an A/C outlet using the supplied wall-wart, and it Just Works. Green light, garage is closed, red blinking light, garage is open. Silent operation, no alarms, just an indicator, which is exactly what I wanted.The so-so:The red blinking LED which indicates the garage is open, could be brighter and more prominent. We are putting this thing in the upstairs hallway so that all members of the household can know when the garage got left open. If we aren't actively looking at it and trying to pay attention, we might not necessarily see it. It's possible to walk by without noticing it. I'm planning to wall-mount the unit at approximately eye-level so that it is harder to miss.The sticky back velcro strips for mounting the transmitter to your garage door are not very strong in terms of stickyness. For instance, if you stick it to your garage door, you can pull on the unit, and the sticky stuff peels off rather than the two halves of velcro peeling apart as you would expect. This made me worry that the unit would fall off the garage door during the heat of the summer. You can work around this if you just purchase some 3M mounting strips and use those instead, or, as I did, use zip ties to reinforce the mounting of the transmitter to one of the upper garage door panel's I-beams (rather than to the flat part of the door panel). As long as the angle of the transmitter is correct and it moves from vertical to horizontal when the door opens, it will still work that way.The bad:The color of the plastic casing is not the same color as shown in the photos here on Amazon. The photos show that the unit is made of white plastic. The unit I received was instead made of tan plastic. I would have preferred white, so that it would match the trim of my home, when I wall-mount the base station in my hallway. I might choose to spray paint the unit to match my house trim before I wall-mount it.The color of the wall-wart A/C adapter and its cord is black. This is not pictured in the photos here on Amazon. This makes it very ugly with wall mounting, unless your walls and trim are black. When I wall-mount the transmitter I may choose to replace the A/C adapter wire with some white colored wire.The place where the A/C Adapter meets the base station is not hidden beneath the unit, it sticks out the top of the unit in an ugly way. This is not pictured in the photos here on Amazon. This makes it hard to wall-mount the unit attractively.The base station has a rather ugly antenna wire that dangles from it. This is not pictured in the photos here on Amazon. If you don't need the extra wireless range that this antenna affords, you might be able to curl it up behind or beneath the base station and still have it work.could not figure out witch plug and transformer to use, when I plugged it in, it lit up once then could not get it to work again may have plugged the wrong transformer in.it was't clear as what to do it