Basically the title, I have sensors at the bottom of the window that will tell me if the window is physically open but it would be nice to know that each window was also locked. Zigbee/zwave preferred
I didn’t find any off the shelf solution, and the location would present a challenge for wiring of any device to look functional. Curious if anyone has a clever approach?
Can you post a picture? People have done this kind of thing a couple of different ways, but it depends on the exact geometry.
Posting a stock photo but I guess it’s termed a sash lock, there are two per window for our setup, at about the 20 and 80 percent mark. You flip them left to unlock and right to lock
Siegenia has a matter over thread smart window handle, but it might be too big for yours. You’d have to check the specs.
(They also have a sensor that goes inside the window frame, but I don’t think that one fits your use case.)
You might be able to do it with a vertical detection beam where the Sashlock being to one side would break the beam, giving you something to detect, and allowing you to put the sensor pieces at the top and bottom of the window frame, but it might look pretty ugly. 
@johnconstantelo might some ideas. 
Thanks the tag @JDRoberts !
Way, way, way back a long time ago I remember it was Andersen and/or Marvin that offered window lock sensors. You had to replace your existing window locks with theirs, and I was seriously taking a look at these. Unfortunately my windows at the time were an aluminum/vinyl construction and wouldn’t fit.
I’m talking years ago when I remember reading about these, and they looked interesting.
I tried searching anything related to his, including archive.org, and came up with nothing, but I really do remember this kind of device a long time ago.
Building something could be possible, but it probably would look bulky and not compliment the window well. Repurposing another sensor is also an option, but that would also be kind of unsightly in my opinion.
Andersen had their Verilock system, including the Verilock Translator, which bridged their proprietary protocol to Z wave. Some people used that with smartthings.
Andersen Windows Connect (Verilock Translator)
However, those products were discontinued about five years ago, and there’s no similar replacement. The engineering was quite good, but they just weren’t cost-effective.
Thanks for digging this up! That’s unfortunate news that it’s no longer supported, but the proprietary bridge also would have been less than ideal..
Agree with your points too @johnconstantelo because the only solution I could think of would look like a huge obvious “wart” on the windows plus some hack to connect… Something … To the actual rotating lever on the sash lock. All without interfering with actually using the window to open it. Hmm.
