Many innovative and useful medical device inventions sense, gather, and display data. However, those inventions may still not be patentable.
A useful example is from the lawsuit in which iLife Technologies sued Nintendo for patent infringement.
iLife owned a patent which evaluated movement of a body based on sensed dynamic acceleration (body movement) and sensed static acceleration (position of body relative to earth).
The court explained that the patent was directed to the abstract idea of "gathering, processing and transmitting information." Even though the patent used sensors for the foregoing, there was no improvement to motion sensor systems, and there was no specific physical configuration of sensors.
Further, the court explained that the patent only referenced generic computer components, a sensor, and a processor. And the patent did not claim any unconventional means or method for configuring or processing the information. Therefore, the patent did not have an inventive concept to warrant a patent.
Take away: to support patentability based on sensors, one should have something unique in the arrangement of the sensors or in the manner in which the sensed information is processed.