Tbh, I put some thought into this one, and I think that the following is something truly not explored enough in Heroes:

In the GN, which is regarded as filler, canon, embellishment, etc, we learn of the girl (name escapes me atm) that senses other's "auras" or astral projections (right? lol). This leads to a hunger to drain the life force of those with abilities. The first ability she acquires is the ability to see ghosts, spirits, angels, etc. THIS, imo is truly the most uncharted territory in the show as far as plot prospects. My theories extend to: spirit communication, and/or controlling spirits or souls(which imo can evolve, in a direction im not too sure of yet, to be on par with that of the petrelli absorbers). By communicating with spirits, one can possibly learn underlying secrets behind the mechanics of the universe. By manipulating them, the world can possibly bend to your every desire. If the writers every take their own creations (the GNs) seriously, they could add so much more to the show

Linda Tavara was the woman who absorbed auras and the woman with mediumship was Ida May Walker (related to Molly Wlaker perhaps?)

Anyway, we don't really know how mediumship worked. Ida May saw ghosts but she never mentioned them spekaing to her and they seemed to show no interest in Linda once she acquired the ability. In fact they seemed completely oblivious to the real world.

By manipualting spirirts you could maybe make them possess people or tell you things about their lives. You would not be able to manipualte the world/reality that's a completely different ability that isn't even in the same ballpark as mediumship.