I'm not actually 100% sure I'm 'joking'. I think we'll see some in-ear haptic feedback stuff in a few years, which take a few more years to get 'right', and will be confusing as heck, but will be useful. If it's customizable, there will be a small but fervent ASMR community around it. It will be pitched as accessibility-friendly, helping people with hearing issues or other sensory issues just 'feel' indicators. Wire it up to 'apple home' and you'll get little in-ear tinglings when certain people come home or leave, or when the garage door opens, and so on. Happy/sad emojis in iMessage will trigger certain ear vibrations, etc.

Having played around with very convincing binaural recording, I am all for subtle auditory haptics as an additional communication layer. I’d be surprised if it’s strictly coded rather than localized to specific objects/interactions within your specific environment.