I've been looking at these too. The Mi store has them for $55 at the moment, quite a bit cheaper that PB tech, though not sure what the shipping is.
Anyone used the function where it maps out your measurements in the App? I want to draw up a plan of our home so that would be quite helpful. Not sure if the map can be exported to a CAD program though. Also not exactly sure about installing Xiaomi software on my phone..