You made me curious...

https://en.wikipedia.org/wiki/List_of_people_who_died_climbing_Mount_Everest

wow, I guess it would be great to be able to use cell/gps technology to communicate with and track a lost/endangered climber

Depending on how high and the weather conditions, it might give a false sense of security. Or it might serve the same purpose as for Rob Hall (https://en.wikipedia.org/wiki/Rob_Hall) in the 1996 Everest disaster (https://en.wikipedia.org/wiki/1996_Mount_Everest_disaster), namely give you a chance to call your pregnant wife and say goodbye. Tragic story.