LOL, having a laugh to be honest! Been there got the Tee shirt! A GPS is a tool although I have come to the conclusion a map and compass are perfectly adequate. As my better half states and probably correct.
Fair enough. However, if you do get lost a map and compass won’t tell you where you are. In poor conditions, such as low cloud or a white-out you will have to rely on technique and estimates of distance covered – the GPS however will tell you exactly where you are. Also, in a white-out a GPS can keep you off the cornice.
What I’d add to that is, the GPS will tell you where you are, but you need a compass preferably along with a map to tell you where to go.
I personally wouldn’t rely on a smart phone as a GPS.
A GPS is not necessary, but if you are out on the hills a lot it's a worthwhile investment.