Just a Hop
There are significant momentum differences between locations on Earth, so the energy needs to come from or go somewhere when teleporting. A newly discovered substance, kinethium, has extremely elastic bonds allowing for extremely high energy density for storage. These bonds are particularly sensitive to kinetic shock, reacting to abrupt changes in kinetic energy by absorbing or dispensing it as needed, up to a point - if the limits are exceeded when absorbing energy, the bonds can be released catastrophically. Fortunately, when doped properly, the material changes color with its energy level, from pale red (low) to intense blue (high), resulting in the frequent comment that when it gets too much energy, it goes "kabluey". As the energy increases, the molecules go from random to tightly aligned, with the result that it also goes from nearly transparent to completely opaque. Only abrupt changes affect the material, and whether it absorbs or dispenses kinetic energy in a field around it depends on the presence or absence of a magnetic field - if present, it dispenses the energy, otherwise it absorbs it. This allows management of the energy - one that's too full, can be impacted inside a magnetic field, or one that's empty and needs to supply energy for a teleport can be impacted without a magnetic field. It should be noted that this capability makes it useful as a general purpose inertial dampener, for example, replacing airbags in cars.
Teleporters have a genetic mutation similar to birds ability to navigate in the earth's magnetic field such that they always know where they are and where they have been. This means they can only teleport to a place that they've already been and have "stored" the magnetic field and velocity vector for the location.
