I have used my cell phone on peaks in the Uintas. I didn't try on King's Peak, but that is because I learned my lesson on another one. Lesson that I learned: never call your wife while you are sitting on a peak. But, I do carry it in the off chance that I need to call, and I can climb a peak and hope to find service. Better than nothing.
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I've taken a vow of poverty. To annoy me, send money.