It appears that the medical products presently available to patients lack a critical energy source.
This is very true for Insulin Pump wearers. If the batteries should go bad, there is no backup available until the user can get new ones.
I propose the use of an energy harvest setup to operate like a hybrid power system where the energy harvester provides operating power during normal activity and the battery is charged. During rest, sleep, or low activity times the battery will provide the required power.
I believe that this would enable the device to operate nearly non-stop with the exception for replacing the insulin vile required.