How it works (pulse-based monitor): The Tomorrow Bio monitoring app, called “Biostasis”, can be installed on an Android phone or an iPhone. In the case of Android, you’ll authorize Tomorrow Bio to access your Google Fit data, which is where the app will be pulling heart rate data from. You have to make sure you also set up your sensor device (e.g., the Oura Ring) to store data in Google Fit. When using Android, you have the choice of any sensor device that can sync with Google Fit. On an iPhone, you only have the choice of the Apple Watch for now. The Biostasis app will pull heart rate data from “Health Kit” (Apple Health). The "pulse-based" Android implementation will wait 6 hours in a ‘trigger’ state before sounding an alarm, and the "pulse-based" iPhone implementation will wait 12 hours in a ‘trigger’ state before sounding the alarm. Find out more by reading the diagram below!
High-level summary of issues: Tomorrow Bio Monitoring App
The above diagram outlines the process through which Tomorrow Bio obtains health data from the Oura Ring (one possible sensor device that could be used with the Android app).
Regarding the iPhone implementation, as previously mentioned, Tomorrow Bio has set the time from a trigger to an alarm on iPhone at 12 hours. This means they will wait for 12 hours after they first notice an absence of heart rate records in Apple Health before sounding an alarm. Why 12 hours, you ask? I suspect the magnitude of this delay was selected because Tomorrow Bio ran into issues with users who lock their phones. A locked iPhone is problematic due to the fact that Apple will not allow 3rd party apps (e.g., the Biostasis app) to read Apple Health data when the user's phone is locked. This means that in the event that the user uses a passcode to protect access to their phone, the Biostasis app has to delay the alarm to accommodate longer periods of the phone being locked. One has to also consider that an iPhone usually automatically locks after some period of non-use. While the phone is locked, the Biostasis app has no records to act on and cannot update its assessment on your status.
Setting an alarm for 6 or 12 hours after a problem is first noticed prevents the user from experiencing too many false positive alarms. Given that the Biostasis app is getting information from Google Fit or Apple Health and that those data logs do not have information on the status of the monitoring device itself (e.g., if the device is being charged, if it's disconnected, if it's in low battery mode, etc.), the app can't actually tell if the absence of heart rate data is due to a real emergency or if it is being caused by the completely normal and benign daily usage of the device. Adding a delay before a real alarm is triggered enables the user to move in and out of Bluetooth range and to charge the device. In the case of the iPhone app, the delay also enables the user to have their phone locked for hours without triggering a false alarm.
Regarding the sensor component, the Biostasis app is only looking for a recent heart rate record in Google Fit (Android version) or Apple Health (iOS version). The app is not looking at raw data or cross-referencing that record with any other sensor data, so it has limited confidence whether there is an emergency or not. It has been observed that most light-based PPG sensors, the type of heart rate sensor found in wrist and ring devices, read a heart rate on an inanimate object at least for some period of time or at some frequency. This means seeing a heart rate entry in Google Fit / Apple Health is not a 100% certainty that the user is actually ok. This choice to only use one sensor's data is the cause of the 'Worst' time in the below chart (Figure 1.2) being as long as it is (48 hrs+).
To summarize the main issues with this overall design/architecture:
Limited health data types: Google Fit and Apple Health only store basic metrics, such as heart rate numbers and general movement data, but not raw sensor data. This restricts the information available for the Biostasis app to assess a user's well-being.
Lack of device-related information: Google Fit and Apple Health do not store details about the device's status, leaving the Biostasis app uninformed about Bluetooth connectivity, battery life, and whether the device is worn or charging.
Sync delays: Delays in syncing between the device and the phone app propagate through the system, which manifest as the absence of heart rate records in Google Fit / Apple Health. This absence of heart rate records makes it look like there is a problem, even though there isn't.
Single (fallible) sensor: PPG sensors (light-based heart rate sensors) are known to be unreliable below 20 bpm (beats per minute) and frequently misread inanimate objects. Because of this, the app may fail the user when they are really in trouble.
How does the system stack up against other current options?
Important (addressing the 'warning' icon in the above chart): The 'Best' time for Tomorrow Bio above assumes that, in the case of Android, the user selects a device with a heart rate sensor that accurately detects an inanimate object more or less immediately and consistently (i.e., for at least 6 hours). I don't currently know of a device that has that ability, but I have not tested them all, and new devices are added to the Google Fit integration list routinely. My testing of the Apple Watch (as best as possible on inanimate objects) indicates it can accurately detect a lack of pulse, but it does not do so consistently (the sensor is not tuned for accuracy in measurement below 20 bpm).
In the average case on Android, when, for instance, one uses a Google Pixel watch, it may read a heart rate on an inanimate object for several minutes or hours. Or it may read a heart rate on one reading and then not on the next. As such, the 'Best' time in the comparison table above is not a common case for the pulse-based version of this monitoring system. In the case of most (if not all) devices the user selects to pair with the app, the best possible alarm delay is likely worse than 6 hours. In the worst case, the delay may be indefinite (or at least until the device loses power + 6 hrs. If the phone is the only place where the user's status is being tracked, the upper delay limit is only true with the additional stipulation that the phone will still have power. If the heart rate readings are intermittent, the device has to read no pulse for at least 6 hours (or, 12 hours on Apple) in order for the alarm to sound. It's possible that a device meets these requirements, but as I have written above, I do not know of any light-based heart rate sensors that, when put on an inanimate object (similar to a human wrist), will always find no pulse. The Samsung Gear 2 is the only device I've encountered that had this accuracy, but this device is no longer available.
I feel as though the risks involving false negative heart rates cannot be overstated, and I am hesitant to put any time numbers for Tomorrow Bio in the above comparison. Thus, please note that if you intend to use this app, you absolutely must consider how your device choice behaves in the case of inanimate objects, otherwise, you could face some very long delays in the alarm system. For example, some of these devices in this YouTube clip falsely read a heart rate for over 3 hours. Once this app moves out of beta, I expect that Tomorrow Bio will help users navigate this issue (though it's a difficult issue, and I would say it's arguably the main obstacle in the way of convenient and expedient monitoring for cryonicists).
Summary: While the Tomorrow Bio monitoring app is still in beta, the difficulties that arise as a consequence of the chosen system design (e.g., choosing to interface with Google Fit / Apple Health rather than running an app on a particular device) cannot be solved with small software changes. Improvements to Best, Worst and Average times will require the app to run on particular devices rather than trying to make the right determination at a distance. In the meantime, backing up your use of the Biostasis app with a check-in based solution, such as Alcor's or CI's app, would be advisable (The Biostasis app does offer a check-in version as well, but it can't be used simultaneously with the pulse-based solution).
Review video coming soon!