Abstract: One variation of the invention is a electronic module comprising: a housing with external faces and electrically-conductive first, second, and third toes, each of which extends from one face to an adjacent face; first, second, and third magnetic elements arranged within the housing and proximal the first, second, and third toes, respectively; and a circuit arranged within the housing and electrically coupled to the toes. The circuit is operable between: a first mode when the first and second toes are in contact with a first terminal and a second terminal of a second electronic module, respectively; and a second mode when the second and the third toes are in contact with the second terminal and a third terminal of the second electronic module. The magnetic elements are configured to transiently retain the second electronic module against the housing, in both stacked and adjacent configurations, in the first and second modes.