While I am a big fan of DIY bio, my experience with Raspberry Pis is that they are highly prone to failure. Becoming dependent on a device- that is, expecting it to work with close to 100% reliability- and then using a device that is easy to disable and prone to failure (I run a fleet of Pis and they mangle their SD cards a lot)- seems like wishful thinking.
It may work 95% of the time, but that's not good enough. There's a reason really good medical devices are based on simpler platforms that are more robust.
I had enough problems running one that was hooked up to the wall, running it on batteries just increases the chances of an SD card/file system failure.
They could make the thing a lot more fault tolerant if they set up its fstab to mount the file system read only, and run in memory.
I've had some mixed success with Raspberry Pi's spontaneously failing as well. This is perfect opportunity for a dual or triple redundancy lockstep MCU to take the place of the Raspberry Pi.
At the same time, this is a really cool hobby project that someone interested in a future developing medical devices could try to replicate as they are learning.
This is an interesting personal project, but it is far from how medical devices should be (and are) developed. Where is the risk analysis, for example? Or the FMEA? Was the software developed under ISO 62304? Etc.
There's a lot of activity that happens in a regulated industry that is completely missing here, which is why I see this as a poor example.
It may work 95% of the time, but that's not good enough. There's a reason really good medical devices are based on simpler platforms that are more robust.