The Stelo. 2 for $99. Oddly, it shipped from Amazon but Amazon doesn't sell them.

The app is subpar on iOS, but if you give Apple's Health app permission, you can get more data in there. Graphs that have absolute numbers. I think they reason their app doesn't give absolute values (for historical values, they give the current value only), is because it's not a calibrated device. It can't be used to control an insulin pump, for that reason.

Does that imply you are paying $99 / month?

No, this was a one-time thing for me, to work out how food impacts my blood sugar. I've used 1 of the 2 I bought, and I plan to use the other in 3-4 months, to see how I react then, after 6+ months with low sugar intake.

I just completed two weeks with Lingo by Abbott. It was decent. I wish it had better integration of the data with Apple Health, but I liked the Lingo score as a way of "gamifying" it and the UX overall was decently done.