There are multiple ways to compare the current choices for cryonics monitoring. I propose the following dimensions for framing discussion on this topic:
What is the shortest possible alarm delay for a given system, and what is the average or expected time.
What is the worst case scenario (when used properly) and the likelihood that the alarm does not go off at all.
Will the user face many false alarms? Does it require a lot of user interaction? Is it accessible?
In order to optimize the above dimensions, we will likely need to build a custom device. Alternatively we may encounter a medical device that monitors for emergencies that checks all the boxes.
In the meantime, how do our current options stack up?
Speed & Reliability
Each of the below monitoring options has its own review article that goes into more depth about how it works and how the values in the below table were calculated.
The above table may give the impression that Gene Shaver's implementation should not be used, but actually, when people ask me what to use for monitoring I always recommend his app + the CI Check-In app. I recommend using both apps simultaneously because their problem detection mechanisms complement each other. Gene Shaver's app is a sensor solution that could very well sound the alarm soon after the user encounters a problem. Unfortunately, we just don't know when exactly that will be due to the variable behavior of the sensor. With its check-in functionality, the CI Check-In app offsets this weakness by providing an upper limit for the problem detection time.
You can read a more detailed explanation of my analysis of Gene's solution here. You can find my analysis of the CI Check-In app here.
In terms of usability, all of the above lend themselves to the hassle of false alarms, even when one takes care to avoid them. Note: the Alcor check-in app is currently only available to Alcor members.
Cryonics monitoring is an area that needs improvement along multiple dimensions, including speed, reliability, and usability. We have major improvements in the pipeline that you can learn about in our 'Projects' section, including our prototype solution 'Smart-Motion on Fitbit Sense', which brings significant improvements in speed and reliability to this space. In the below table, I group Alcor and CI check-in apps due to overall similarity. Note that the row "Tomorrow Bio" refers to the pulse-based option of their 'Biostasis' app.
How our 'Smart-Motion On Fitbit Sense' solution stacks up: