No, Im not Richard Harris, pulling a boat with my homies down a dry river bed, looking for water.
But I am wondering what all an iPhone can and cannot do in the wild w/o data access available? Will the GPS work? Will my Topo app work as well?
Thanks in advance.

I don't own an iphone but i have friends who bring them along all the time. Short answer is yes - The GPS and maps work in the middle of nowhere. We used an iphone for our GPS on a sheep hunt in the Brooks range and routinely use them on Elk hunts on Afognak Island (the phone part of the iphones does not work in either locations). My friends do comment about battery power but as far as I'm concerned I think the iphone made the stand alone GPS obsolete. Patrick

I use the MotionX app for my GPS... you can download many types of maps at home on your wifi. Then they'll be there regardless of if you have cell signal.

It will eat up your battery pretty good over the course of a day if you just leave it running in bread crumb mode. You can get those external batteries that will give your phone a couple full charges (test first to see).

I looked at the newest handheld dedicated GPS's last year and opted to use my iPhone and my old SportTrak.

I've downloaded some maps but they eat up the battery so fast that they aren't worth messing with. A pair of rechargeable AA's in my Garmin gps will last 2 days or more.

try Gaiagps- it's $20, but $ well spent- you download 24k:1 topo maps (or different sizes or even satellite maps) for whatever area you want, simply name them and save them

before heading out, load the map you need- turn the phone to airplane mode- this prevents the battery from getting eaten up, but the gps still works; I've had my iphone 6 last 4 days w/ battery life left- that using the map app daily and taking lots of photos

tracking will eat battery life quicker; I only use tracking for very short term or on day outings

I've ditched both my camera and gps in favor of the iphone- do invest in a good weatherproof case for it though

Iphone will work, but the battery is an issue. Not only do they drain fast, if its cold they are always trying to shut down when the battery gets below 50%.

They work and I use mine all the time with OnX, just because I have it with me all the time anyway.but a garmin is much more reliable.

I have not tried using my smart phone for a GPS but the large screen would be much nicer that my Garmin...

Just got back after spending 3 days in the breaks.

I use Hunt onX app and it works great. Download the maps in advance. Turn off wifi, bluetooth etc and turn on offline maps option in the app. I believe you can also shut down the phone's attempting to find service, but I didn't. Only time it really ate batteries was when I turned on the tracking. Otherwise it was fine. I had property ownership, topo, sat image, government lans etc. Can overlay hunting districts, etc.

I typically shut the thing down for a majority of the time anyway and that helps also. I did have a couple small battery packs, about the size of a roll of lifesavers as a backup.

With all that said, I am considering buying a gps to pack and use as they are a lot cheaper if you break or lose it. Then I would have the iphone packed away securely as a backup.

Airplane mode shuts down wifi, bluetooth, searching for service, etc., all in 1 easy step. It does leave the gps running.
The more you shut off, the longer the battery lasts.

That said, a dedicated gps that uses AA batteries is much easier to keep running in the back country.

I've hunted for days with them. But, I don't use the tracking feature. I simply use it as a locator in 'Airplane' mode. Obviously, you have to get your maps right beforehand.

^ same here- 4-5 days in airplane mode with judicious use (and turning off at night)

I usually carry a Black Diamond Ember Light flashlight- it's a small 150 flashlight, but can also provide a full charge on your phone

http://blackdiamondequipment.com/en_US/headlamps-and-lanterns/ember-power-light-BD620801_cfg.html

I use my iPhone for most photos, texting, etc if in cell range ..which is often high up. I also use it for mapping via the Delorme inReach app which does not require cell reception to work. I then pair it with the inReach if I need to send messages and am not in coverage. I have also started using a headlamp that recharges via USB , and carrying an larger Anker Powercore battery.

I can get 2 -5 days off the iPhone depending on usage. Usually 5 days per inReach charge once again depending on usage. With the Anker I can get 4 phone recharges ... or probably 3 and an inReach recharge ... or probably 2 phone / 1 inReach / several headlamp charges. I sleep with the phone in my pocket or in my bag, the headlamp on my neck , and if I am using the inReach , then often the inReach in my bag. I sometimes even upload directly to Instagram or Facebook in the wilderness (I know sort of anti wilderness there ... but it's also sort of part of the gig ).

These days, I prefer to use a map with a UTM grid that I print magnified to my area of interest WITH a matching paper grid/ruler that I cover with transparent tape. With UTM, however, the coordinates are already equivalent to meters so there is no ruler/scale required when you already have a grid.

My iPhone's battery drains ridiculously fast so I am moving away from depending on it and I also do not have a separate GPS.

What I still do use is an app called "Toms Trails" that simply dumps GPS coordinates in UTM. This is as spartan as one can get to minimize battery-dependence but still provide the most basic benefit/advantage of a GPS device, placing your position definitively on a map.

Save battery time: put it in airplane mode, turn off sound & vibration AND reduce screen brightness. If you can, choose an app with black background only and mostly minimal, text-based.

Use https://mappingsupport.com to get free topo's on your desktop computer with your grid of choice and print them out. Note lack of magnetic declination on printout so you have to look that up separately: http://www.ngdc.noaa.gov/geomag-web/#declination

I run a solar charger....