Even if the device would be much less precise than claimed in the paper, it would still be good enough to save the lives of many people.
One can always measure the blood pressure with a classic instrument every few days and recalibrate the tattoo resistance measurement.
What is important is to be able to measure the blood pressure continuously and trigger an alarm whenever it becomes too high or too low.
My mother died a few years ago, precisely because I did not have such a device for continuous blood pressure monitoring. Having her arm compressed was painful and very unpleasant for her, so I could not measure her blood pressure more than once per day.
She had a very dangerous condition, where she needed to take some medication to avoid a too high blood pressure, which could cause a hemorrhagic stroke, while simultaneously taking high quantities of salt and potassium supplements, because she eliminated them too quickly, so in a very short time she could reach a too low sodium/potassium content in the blood, which would trigger severe neurological problems.
It was very difficult to balance the 2 kinds of medication with contrary effects and every day their doses had to be adjusted.
Without continuous blood pressure monitoring, the daily doses could be based only on guesses, taking into account the recent history.
With great efforts, her health state has been kept stable for a couple of years, but then one day, for unknown reasons, she had a sudden fluctuation in the blood pressure, which became double the normal value, so soon she had a fatal stroke.
With continuous blood pressure monitoring, an alarm would have allowed the immediate use of blood pressure lowering medication, which could have prevented the stroke.
Therefore I believe that the development of such devices is very important, despite their shortcomings.