I think a sat phone would be overkill. While you are in an official wilderness area, the kaibab/bright angel trail system is heavily used. For me, that is its principal disadvantage. Solitude resides elsewhere in Grand Canyon.

On the other hand, the trail is so good that you should have no trouble getting a real early start and following the trail in the dark. I have started Grand Canyon hikes as early as 2:30 AM - the desert equivalent of an early alpine start. If the moon is up, you really don't need a light. <img src="/forums/images/graemlins/grin.gif" alt="" />