A system and method involves a machine having a power train including a continuously variable transmission associated with a plurality of virtual gear ratios. The reference circuit includes at least one controlled current source. The skin engaging surface is generally non-flat with generally coplanar portions, and a recess being defined in the skin engaging surface which defines a void in or adjacent to the coplanar portions into which portions of a patient’s skin can be deformed into when the skin engaging surface is pressed against the patient’s skin. A first processor at the monitoring station is programmed to determine, for each of the GPS receivers, whether said GPS related data deviates from any of the at least one GPS parameter by more than a predetermined range of error, and for issuing a warning in response thereto. When a schedule entry which has been dormant becomes active, its one or more timestamps are typically initialized, which may include setting at least one of these timestamps behind current time by a wakeup burst tolerance value to guarantee its immediate eligibility for one or more consecutive scheduling iterations.