Today I mused about a literal heatmap with my colleague Caroline: could you project infrared light of differing intensities in a 2D pattern onto a surface, creating warm spots that would allow a user (perhaps visually impaired) to feel a spatial pattern?
I also speculated about whether you could have an array of tiny speakers, putting out sound of different intensity/frequency in different zones. Not sure if human hearing would be sufficient to get much of a pattern out of that, though?