It's pretty simple to tell whether or not a sensor uses a reed switch you simply listen to it. With such a device you'll hear a quiet but perceptible click as you bring the magnet close to the main body. And it's by doing this that I'm able to tell you that the FGK-10x like most door and window sensors does indeed use a reed switch.
So far it all sounds a little conventional, but there are a few reasons why this particular device is interesting. For starters, it doesn't quite have the "ugly box" form factor of many of its competitors. The main unit is index-finger-sized, and rounded rather than square. The magnet is tiny.
But interestingly, this sensor comes in a range of colours. If you have a dark brown door frame then a normal white sensor will stick out like a sore thumb, but you can order the FGK-10x in dark brown. In fact, the "x" in the product code isn't really an "x" at all (although this is how the device is usually referred to) it's replaced with a number. FGK-101 is white, 102 is grey, 103 black, and so on. A dark brown one would be FGK-107.
The other reason the device is interesting is that it has additional inputs. There's a binary input that you can connect to a volt-free contact such as a push button. Note, though, that this input is wired in parallel with the internal reed switch, so it isn't really suitable for use as, say, a door-open contact and external doorbell push at the same time.
More usefully, there's also a temperature input you simply need to connect a DS18B20 (a three-pin device that looks like a transistor). These are readily available and cheap so cheap, in fact, that it's a pity Fibaro didn't just include one in the design.
Battery life should easily be over a year in most situations, which is good since it takes a not-that-easy-to-find ER14250 battery; it's half the size of an AA, but pumps out 3.6V. In summary: the FGK-10x is an interesting device, and certainly different from most other door sensors, but it still might fail Josh's "ugly" test, so let's move on.
Paint your own
Next out of the box of goodies from Vesternet is the Door/Window Sensor 6 from Aeon Labs' Aeotec range. This one certainly isn't an ugly square box it's triangular! Imagine a pub beer mat folded in half across the corners and that will give you a rough idea of the size. It's only 9mm thick, so much thinner than traditional sensors.
The triangular form factor means that it can fit discreetly into the corner of a door or window you'll hardly notice it's there. The supplied magnets are incredibly small too. Aeon Labs describes them as "shards", and that's a great name since they're barely 2mm thick. The obvious difference between the Door/Window Sensor 6 and a more traditional sensor such as the Fibaro above is that normally you'd attach the sensor to the frame and the activating magnet to the door or window, but with this device it's the other way around. This obviously means that the sensor needs to be more robust, as it will get quite a bang when a door slams. It seems to be up to the job, though, and the super- light weight helps in this respect.
Unlike the Fibaro, it isn't available in a range of colours only white. But the case of the sensor is made from a special matte plastic, which is designed to be painted, after which it becomes pretty much invisible. It's such a simple idea that it makes you wonder why other sensors are made from that shiny plastic that's almost impossible to paint.
Another point of departure from the FGK-10x is that the Aeon Labs Door/Window Sensor 6 uses a fifth-generation Z-Wave chipset, usually referred to as either Gen5 or Z-Wave Plus, depending on the manufacturer. The major benefits are greater range and battery life, although increased bandwidth and better noise immunity are important too. Most of the sensor manufacturers are slowly updating their product lines to include Gen5 capabilities.
Unlike more traditional sensors, which have only a single point of activation, the Door/Window Sensor 6 includes magnetic detectors (reed switches you can hear the faint click) on both of the shorter sides of the right-angle triangle. This means there's plenty of flexibility when it comes to mounting the device.
One really interesting aspect of this little triangular sensor, and it's one that you don't see often in this type of kit, is that it uses a rechargeable battery. In normal use you should get between ten months and a year from the sensor; when your home automation system starts to display battery warnings, simply unclip the sensor from the door or window and recharge it using a standard micro-USB phone charger. It even comes with a micro-USB cable in the box. A full charge takes a few hours, so obviously you need to arrange to do this at a time when the sensor isn't needed for security reasons. The lack of removable battery is partly what helps with the robustness mentioned earlier give most removable-battery-powered devices a knock and it's usually the battery that goes flying.
