[neek]

I hate mobile phones as much as the next self-respecting Luddite, but admit to using them more and more for outdoor activities. I thought it would be fun to put together a list of uses for these devices beyond the obvious one of GPS navigation. Some of these are more whimsical than serious, but things are changing so quickly that what seems silly today might be common tomorrow. It goes without saying that a phone is no substitute for experience, paper, common sense, specialized safety equipment, etc. Please feel free to add items I missed.

1. GPS. See where you are on a pre-loaded topo map. Follow someone's track. Create your own. Track your stats on one of the many social apps that make it easy.
2. Compass. Magnetic compasses in modern phones still must be calibrated frequently, but don't drain the battery like they used to.
3. Altimeter. Your phone has a very accurate barometer that makes carrying a separate altimeter unnecessary (except for redundancy). I haven't found any map apps that take advantage of this underappreciated feature, but they should. I use a simple app called Barometer+ to sync with the sea-level pressure reported by the nearest airport and tell me exactly how high I am. It's important to find an app where you can set this manually, for cases where you know your elevation but don't have an Internet connection. A barometer is the only tool I know of that will give you accurate elevation gain for trails that have lots of minor ups and downs. GPS elevation is notoriously inaccurate and jittery.
4. Flashlight. Kinda ghetto, but much better than nothing.
5. Clock. Duh. Also, timer/stopwatch/alarm.
6. Walkie-talkie. More like...you should be able to do this, but can't really. There are Bluetooth apps with a supposed range of 100 meters, but in practice I've found it to be much less. This would be great for people, say, ascending parallel gullies, but rocks block the signal.
7. Beta. Pre-load your phone with maps, trip reports, photos, and anything else that will help you navigate. I'll often send a summitpost (or nwhikers!) URL to Pocket and have a nice offline copy of the content to refer to.
8. Slope angle meter. "Angle Meter" and similar apps tell you how much the phone is tilted, very accurately. Just line the phone edge up with the slope.
9. Camera. Obviously. Aside from just taking pictures to view later, they can help you during your activity. Take a route overview shot and then refer to it while you're on the route. Turn around and take a picture to aid with backtracking! Also, note that you don't have to remember what you just took a picture of. Your phone will geotag it (although be aware of this if you post to social media). And you can add a caption right there, possibly using the voice recognition feature rather than that impossible on-screen keyboard.
10. Step counter. There are apps that do some math on gyroscope and other sensor data, and give you an accurate count of steps taken. No need to carry that old Fitbit around.
11. Notebook. Take notes with voice dictation - about the hike itself, or any random thing you might be thinking about.
12. Mirror. Put it in selfie mode to help yourself dig that bug out of your eye or moonrock out of your nose.
13. Location recorder. Don't count on having a signal anywhere - a phone doesn't replace a locator beacon. But at least take it out of airplane mode briefly while on a ridge or a peak to hopefully generate a "ping" if there's a later issue.
14. Plant identification. Take a picture of a plant and have AI identify it for you. OK, maybe this isn't possible yet, especially while offline, but I'm sure it will be someday.
15. Bird song identification. Same deal. One of these days...
16. Light meter. I haven't yet figured out what this might be useful for. Determining how likely you are to get sunburn or snow blindness?
17. Antisocial device. Pretend you're talking or texting so you don't have to say "hi" to people you pass. (I do this all the time downtown to avoid making eye contact with solicitors.)
18. Trip report submitter. I've written trip reports on the drive home (when someone else was driving of course). A lightweight portable Bluetooth keyboard can help.
19. Citizen science. I'm sure there's a ton of potential here. I was just reading about a magnifying lens that attaches to the camera and lets you submit photos of snowflakes for atmospheric study - cool!
20. Entertainment. Music (with earphones please), books, games - yeah, you're out in nature, but while camping in the dark season, nights can get awfully long. A portable battery pack is IMO more useful than one of those solar charger dealybobs unless you'll be out for more than say a week or two.

Anything else? I'm always looking for creative ways to get my money's worth out of stuff I'm forced to buy. Another tip: put a label on your phone with your contact info. Most hikers are nice and will help reunite you with it.

[Cyclopath]

I enjoy Google Sky Map when I'm backpacking. What star, planet, constellation, etc am I looking at?

[Schenk]

#21- Fire Starter. A cell phone battery (not dead) and some thin gauge wire, steel wool, or even foil (think: gum wrapper), can be used to light tinder.

[Cyclopath]

[Pef]

A non-voluntary suppository if you insist on using it to play your music without a headset within my hearing distance.

[Bronco]

Peakfinder app is pretty nice to have in the mountains.

[DigitalJanitor]

WEATHER: reports via browser + Doppler via aps like Rainy Days, if within cell range SUNDROID: I have the pay for version so I can know how long to both sunset and civil twilight

[reststep]

[Jaberwock]

[Adohrn]

A tip if your using it for weather forecast and using an iPhone. Instead of bookmarking use add to reading list which saves the whole page for offline use. That way you don’t have to rely on your faulty memory. Apps like the weather underground sooner or later time out without renewed cellular contact, and the forecast page goes blank. Grrrr.

[puzzlr]

A look-for-it set of photos. On a couple recent hikes I've brought along some old photos to see if/how things had changed in the 10 years since my last visit. Also, a couple of photos others took of special trees that I had missed and wanted to find.