In the future technology reaches the point where human mind emulation and upload becomes possible. However, it becomes clear that the human mind and psychological state is tied inexorably to the physical world and physical experience. Human minds in a pure mental state go insane and need the constant stimulus of real-world interaction that only existing in a physical world can bring.
Human minds can’t be downloaded into flesh as the structure of the brain and the technology to actually build one from scratch that will represent the mind doesn’t yet exist, so life after death or body transferral doesn’t exist. However, a new kind of technology presents itself.
Hitch-hikers. Minds without a body that hitch-hike on other, real people’s, real world experience as their actions and stimuli are copied and streamed to the eager, hungry digital minds. Hitch-hikers get to live other people’s lives as a passive observer while having their minds free to do other things. Obviously someone else’s entire sensorium is quite distracting, not to mention the obvious privacy concerns, so the visual and auditory senses are disabled.
Meat-space people can sell their sensoriums as subscription services to digital minds and minds can subscribe to more than one, switching between sensoriums at will. Hitch-hikers can experience the life of a child, the opposite gender, a dying person. Sensorium pornography becomes huge.
Publicly licensed sensorium feeds are anonymised so the subscribers can’t find out who they are subscribed to but ones contracted privately are bound by no such restriction.
Story ideas for this include privacy concerns, body-hijacking, the effect of the dead still living digitally as parasites on the living on society, what happens when a mind falls in love with the person they are subscribed to? Lots of various things can be done with this and you’ve got a good “two different worlds” motif going on with the digital, mental-only world of the hitch-hikers and the physical world and how denizens of both interact.