Thanks for brings this back to the top of my todo list.
I tried the bluetooth option, never installed the app, it wouldn't install without access to contacts etc
Just ordered this for more than $40 but a lot less than the $200 - $400+ for the other 6 sensor systems.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
FYI the same display is for sale at a much lower price BUT they use INternal sensors