[davidthewatson]

Yes, thanks for asking.

Continous Glucose Monitors (CGM). That used to be a diabetic-only problem until Abbott, Dexcom,and other vendors expanded their markets beyond diagnosed diabetics into pre-diabetes markets and exercise, health, and well-being applications like:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10635370/

and:

https://www.levelshealth.com/

This has exploded beyond the hundred years of ketogenic research and as research on glycemic variability in mental health has grown.

My current kit includes an Apple Watch series 9 and an iPhone SE. Prior to that it was Google Pixel and a Fitbit Sense, though direct BTLE->Watch was not an option in that generation.

I have two complications: Abbott Freestyle Libre 3 and Dexcom G7. Continuous Glucose Monitors (CGM). The Dexcom is entirely proprietary. The Abbott is accomplished via a series of 3rd party hacks:

https://www.youtube.com/watch?v=YqUZjXo5VXY

I'd say open source, but I'm not certain that every link in the chain is open source. I've run many generations of various open source tools on Android and iPhone since no vendor ships a complete end-to-end solution that is perfect.

Nightscout and watchdrip are two open source examples:

https://nightscout.github.io/

https://watchdrip.org/

When G7 originally shipped last year, sensor data left the sensor and used the iPhone as a proxy-to-cloud storage, as has become the default mode across many IoT devices because it was easy, obvious, despite the unintended consequences of the design choices here.

At that point, because the data has already taken a long and perilous journey into cloud when BTLE->Watch was dramatically shorter, cheaper (in terms of hops and requirement for service), and arguably better. Hence, any data request pays that full routing price into and out of cloud, even the most trivial display, such as watch.

After a latent Dexcom BTLE->Apple Watch update a year later, I don't even need to carry my iPhone anymore, despite the fact that I don't have service beyond WiFi on my Apple Watch, since the data exchange is entirely BTLE.

The sad fact is that straightforward questions around a person's glycemia were not answerable directly without an entire belt-worn cloud ecosystem being paid for and fully functional 24x7x365.

BTLE->Apple Watch is by no means perfect, but it's dramatically better than my previous 5 years of 24x7x365 routing through cloud.

HTH!

[raihansaputra]

i'm kinda interested in doing that too. do you wear the CGM all day? what's your recommendation? looking to link to my Apple Watch as well if possible.

[davidthewatson]

This is a short book. My apologies.

You don't really have a choice with current gen CGM as to "all day". These devices are designed to be inserted and used on either a 10 day cycle (Dexcom) or 14 day cycle (Abbott).

Also, be sure "kinda interested" can handle "wrong most of the time" or "better chance of survival" as in T1D or T2D. There's no question that the data are aligning around glycemia as an influencer of everything from mental and physical health to the brain's default mode network. We used to talk about DMN as if it were much more immutable than it is. The deeper the neuro-imaging goes, the less true that seems.

LSS: glycemia is a significant influencer of behavior, not the only influencer, where the direction and slope of the glycemic curve determines the influence and that slope is more exaggerated with metabolic disorders like diabetes because insulin may not be a pill, but it's side effects are far more dramatic than most when taken exogenously without broad and deep knowledge of the pharmacokinetics and their impact, which are not well-understood outside the MD-PhD realm.

But I digress.

Once the device is inserted, it begins working after a warmup period, enforced by the software, of either an hour (Abbott) or 20 minutes (Dexcom). It's worth noting that I've seen data veracity and device reliability change with the same generation of devices, but software updates more frequent. I suspect this is due to changes in the software since nothing else has changed in the devices or the environment in which they operate.

My recommendation is to WAIT as long as possible prior to engaging with current CGM.

Why?

Because the last 5-10 years were the "ship the prototype" phase common in big tech.

Given the history, I'd expect the 2025-2030 3rd or 5th generation devices to be amazing, though their dependence on the smartphone ecosystem should be duly noted as good marketing, but perhaps an "embrace and extend" in which realtime blood glucose cannot be known without not just the phone, but the 4G or 5G network behind it at significant cost to the consumer.

This is why Dexcom's "innovation" of fixing the design mistake of routing local data through cloud and back to the display device is significant. Until other manufacturers follow suit, it is the only device I own that can do this direct BT device -> watch data exchange WITHOUT a costly smartphone ecosystem playing cloud proxy in the middle. There may be others.

The significance here cannot be overstated precisely because it enables things like running or biking with a non-cell enabled watch without carrying the phone as cloud proxy via crappy wireless networks. Prior to this, that would have worked if and only if the watch had direct cell capability above and beyond BT or WiFi, assuming some things about the software which I'm not sure are correct.

I just wanted to be clear that the BT -> watch in this wearable health data sensor paradigm is only possible with Dexcom presently to my knowledge. Shipments may invalidate that statement tomorrow so one can only hope.

In the meantime:

Caveat emptor.