A computer-implemented system and method for triggering events based on user location with respect to zones of influence is described. The device comprises: light sources to project two-dimensional first and second light distributions in respective first and second planes; and a multi-pixel sensor system to remotely detect touch of an area of said surface within or adjacent to the displayed image by detecting light from the first distribution to provide a detected touch signal. Different protocol effects might be changed in response to one or more said thresholds, with the effect that distinct wireless communication systems may operate in relatively close proximity with a minimum of interference. In order to separate the negative electrode and the negative electrolyte solution from the positive electrolyte solution, the cell includes a sodium ion conductive electrolyte membrane.