Related rant: I wish I could get my hands on one of those fancy continuous glucose monitors to correlate my findings. Damn hassle in the US with prescription and all.
This was not one of the fancy kinds that are usually integrated with an insulin pump. It applied to the back of my arm.
Now I poke my finger 2-5 times a day. It was nice having data on my phone that I could look at, but that data was still locked to my device and not exportable so it was worthless.
I use Google Sheets to keep track, and I can do it anywhere AND do something useful with the data.
Look at the hardware lists of open source projects in this space:
https://openaps.readthedocs.io/en/master/docs/Gear%20Up/CGM....
https://androidaps.readthedocs.io/en/latest/Module/module.ht...