As I wrote in the title, I’m not sure I understand what are the advantages over using a simple ESP, aside from better electrical design?
IMHO: in combination with Home Assistant the only advantage they offer is that it is an out-of-the-box solution.
Typically alarm sensor monitoring also checks for tamper, cable cut or short using resistor measurement. This does require some work to set up with your ESP and konnected.io has this built in.
That, and your ESP doesn’t have a fancy website promoting itself 
That said, konnected.io is more geared to people who are not really electronics enthousiasts but can manage replacing the PCB in an alarm system. The hardware is made to look similar to a traditional system.
Thomas
Something that often gets overlooked is the value of time in projects (lost opportunity costs), and this is a determination that each of us must make and will vary greatly from person to person. In my case, paying $99 for a well-designed compact interface board that allowed me to bridge existing wired sensors from my alarm panel in a matter of minutes in a clean and neat wiring closet install, match the resistance level with a turn of a screw with visual LED feedback, and then to transmit those sensor states in near instantaneous real-time to Home Assistant was an easy choice. Plug and play and I was done, and I could use my time for things I enjoy more.
Similarly, I needed a leak detector sensor the other day, and created one from a Wyze Sense contact sensor. It is about the size of a quarter, took 15 minutes to create by soldering two small wires where the reed switch was mounted and folding the wires under the sensor with the tinned ends of the wires exposed, and cost all of $5 and works great. But, if Wyze had their own leak sensor available for $10-$15, I would have bought it instead.
Totally agree with this. I had several DIY-interfaces in my installation and have replaced nearly all of them by off-the-shelf hardware because of the time it saves.
Bottom line, there are two approaches:
- If you are in it to “build an learn”, by all means go the DIT-hardware route.
- If you don’t really care about that part and are in it for the software and/or the end result, then buy off-the-shelf parts and integrate them.
Both are equally valid but different.
Thomas
Ok, so it seems that I hadn’t missed any crucial detail.
Yes, I did consider the time expense in my evaluation, and I’m still a bit torn. I do value my time and 180€ is cheaper than my labor cost would be but I can’t help feeling it’s a bit steep for a microcontroller board, after all I do enjoy this kind of tinkering.