I got mine today. I ordered from Aliexpress and it shipped from the US via Amazon. I paid less than one hundred shipped, so it was a pretty good deal to me.
I have nothing but the Photone app to compare it to, but it is within 5 points of everything that the Photone app shows with a regular paper filter (iPhone requires it). For me, it is so much easier to use in my nano vs vacuum sealing my phone and trying to get it around the rocks and corals while holding it flat. The meter's sensor is much smaller and easier to move around with the included "stick".
Overall, I'm pretty happy with it. Granted, it is one of those things that I'll use and then put on the shelf unless I change lighting schedules or lamps. More of the reason that I didn't want to spend hundreds on a fancy one.