For characters with technology analogous to the Hitomi (e.g. cell phones, golems from the DGM universe, etc.), that item is usually turned by the gods into a Hitomi. So for your character, this omni-tool would remain looking the same (as the Hitomi can change form to what your character finds most useful to use), but any functions outside of the Hitomi's map/GPS system and the network would be disabled.

As for the life support function, high-level technology does not exist in Kannagara, however! The gods are fair and will equip your character's omni-tool/Hitomi with an equivalent system that works exactly the same, but runs on the magic which empowers the Hitomi. As a side note, the Hitomi are not hackable by any means with any level of technology.

We hope this clarifies some things!