My phone was supplied with a power button. Fairly easy to turn off and still carry.

iPhone in an Otterbox, center jersey pocket.

over 30k miles without any problems

It's an older phone, so not as big as a smart phone so, I slide it into my smallish saddle bag. If raining or if I know that it might rain during the ride, I'll put it into 2 ziplock bags first. I really don't like anything more than a Clif Bar or 2 in my jersey pockets.

+1, although I do carry a ziplock if it might rain to stick the phone in.

Jersey pocket. Since sometime between 1996 and 1998 when I realized I was never home to answer my land line and was working for Qualcomm who made CDMA phones. No problems.

FWIW if you're lying unconscious in a ditch because some ******* ran you off the road leaving your cellphone on (you can turn off the ringer if you want) will help them find you (even without GPS they can pull the records of which towers your phone was talking to and triangulate on your position).

Obviously not.

In an e-pack.

Yes, exactly that happened to me three weeks ago. Crash, concussion, didn't know how accident happened, nor how I ended up in the policeman's car, nor how my wife learned where I was, nor why I refused to get in the ambulance that came later. A passerby stopped and used my phone to call my wife (and police?). Don't remember, but I vaguely recall having given her the number. Zip bag, phone in pocket, all the time now! I used to be like Velo Dog. Hard to be self-sufficient when you are out cold and lying on the road.

Yep, even though I don't answer calls while I'm riding (not least because I don't often hear the phone over the wind and road noise) it's useful to be able to be reached. Like the time my wife couldn't get into the house because the front door lock had jammed it was useful for her to be able to call me to tell me she needed help.

Oh For the love of God, use your brain.

I've tried it, but the GSMC antenna doesn't want to authenticate my brain's signals

I thought the comment was referring to using ESP to make contact if something goes badly wrong. I think a phone has more science behind it.

Latitude gives an approximate location. Real Time GPS Tracker let's someone else know EXACTLY where you are, along with how fast you're moving and how much battery you have remaining. My wife keeps an eye on my rides. If I'm stopped for more than a few minutes she texts me to make sure I'm ok.

only an idiot would ride without his phone.

same goes for I.D.

Which is great, as long as you're using an Android phone.

Latitude is far from perfect but usually provides enough information for my purposes. I don't really care if someone else knows my precise location, if I'm going any distance to visit someone they'll have a good idea what route I'm taking and if it all goes pear shaped they'll have an idea of where to expect to find me based on that.

Inside a ziploc plastic bag inside my saddle bag. Figure that's the safest place for it. Shouldn't get wet if it rains and little (no?) damage if I fall.

In a Jersey Bin in the middle pocket of my jersey.

I use this for my Nokia. Note that this is a pretty old phone, so it's smaller.

https://www.topeak.com/products/Bags/PDAPhonePack

really so you are saying people never rode bikes before cell phones .......and for people riding across the US if they have no signal they should stop until somebody builds a tower or risk being called an idiot by you the phone expert

On the wall in my home

This.Just a little snack bag works perfect. Then right into my jersey.

Left jersey pocket...ziplock bag if it's raining when I leave.

if you have one, ride with it. only a wilful idiot would choose to leave it at home.

Don't be dense...if you have the ability to carry a cell phone while riding, you should. Turn it off if you must, but there is no reason not to carry one if you have one. It goes along with wearing a helmet, carrying ID, and obeying traffic laws. You should just do it because it increases your chances of returning from your ride alive. At the very least establishing a habit of carrying your phone when you ride will give the people who care about you a little peace of mind when you disappear for hours at a time to go riding alone.