Interesting point. I looked up Canadian and American data and it appears that 7% to 10% of population are hospitalized at some time each year. Multiply this by the number of sensors per patient  and divide by the shared uses per year for a device, and I think there may be a requirement for around 7% to 10% of the population in total devices. This is probably larger than current use of smart matches, but its largely in the same order of magnitude.