Although the term 'Heterostasis' is an obvious rearrangement (by syntactically substituting the prefix 'Hetero-' for its dichotome 'Homeo-', and likewise swapping the semantic reference, from 'same'/'single' to 'different'/'many'), the endocrinologist Hans Selye[1] is generally credited with its invention.
An excellent overview of the two concepts is contained in the Cambridge Handbook of Psychophysiology, Chapter 19.
[2] Selye's ideas were used by Gunther et al.,[3] in which dimensionless numbers (allometric invariance analysis) were used to investigate the existence of heterostasis in canine cardiovascular systems.
The equivalent term Allostasis is used in biological contexts, where state change is analog (continuous), but Heterostasis is sometimes preferred for systems which possess a finite number of distinct (discrete) internal states, such as those containing computational processes.
The term Servomechanism is usually used in industrial/mechanical situations (non-biological and non-computational) where it often applies to analog state change, e.g. in a Direct Current Servomotor.