Great thread-- and yeah, I've got to cram that space blanket into my under-saddle bag!
My situation is really strange, because I'm in a dense urban area, but I go places that few people know about, and that I only discover via satellite map or hiking or mtb websites. I could have an accident only one to five miles (at the most) from civilization, but still have no one find me for days if I were knocked unconscious in exactly the wrong spot, or forgot my mobile, or if it got lost or shattered, or if I happen to be in a dead zone, all of which are quite possible.
This does creep me out sometimes. I rarely forget my phone, but it happens. I was on a power line access road yesterday just outside Griffith Park in the Cahuenga pass... only 1.5 miles from the nearest house at most, helicopters are flying around, I can see the freeway... but if I fell in certain spots, I would be invisible. I could scream for hours, no one would hear me.
And I've never seen a soul on that trail, ever. On Brand Park Motorway, it might be hours before someone else comes by, but unless I'm the last person coming down the mountain (possible, but not likely) I'm going to run into someone. I also occasionally detour briefly through alleys, abandoned bike paths, and short but creepy little trails in Atwater Park... places where I really don't have a sense of what the crime situation is-- if someone mugged me and I was unconscious under a bush or behind a dumpster, someone would probably find me sooner, but maybe not soon enough.
So what I consider 'remote' is a bit different! And my precautions wouldn't be right for everyone.
* I'm almost always alone, I have only one friend my age who sometimes rides with me on my second bike, and he's only around 4 months of the year.
* Tire sealant kit.
* Some tools, even if it's just a bunch of hex keys and a leatherman knock-off.
* Warmer clothes-- extra turtleneck in the under-seat bag, microfiber surf/rash-guard shirt stuffed into a jacket pocket for a little more thermal protection or lightweight UV protection. If possibility of rain is greater than 10%, substitute a packable poncho for one of garments in summer, when I'm not already wearing a water-repellent jacket.
* 12 oz. water bottle in cage for rides < 20 miles. Rides > 20 miles, I'm adding a second 12 oz. water bottle in a cross-body sling.
* Mobile phone, fully charged.
* Front light and helmet rear lights, always fully charged if I'm off road for more than 1/4 mile. (I always get home later than I planned!)
* Body armor every ride-- motocross mesh outer jacket (2 pounds) in the summer, armored lined jacket (4 pounds) in winter. (This is because of the blood thinners.)
* Gloves-- may seem obvious, but again, every ride, even if it's 90 degrees out. Usually fingerless except when it's really cold, winter gloves are armored as well.
* Wallet with at least one credit card + ID and health insurance card.
* Whenever I'm more than 1/2 mile or so off road, I let my wife know exactly where I'm going, and give her a vague idea when I plan to return.
* ALWAYS check weather.
* A new thing: I am now checking the grade of trails I am riding (if possible) on hikingproject.com or mtbproject.com, though it's taking me a while to learn what they mean. For me, it means I can manage up to 23% if it's a really short segment, or mixed 10-20% for a quarter mile segment unless the trail is so primitive that it's not even really a trail. Because I'm very inexperienced at MTB, I also try to have a sense of where the steep sections are, particularly if they might be hard to see ahead of time. If those are the numbers, my worst case scenario is I'll have to push the bike a bit.
* When mobile service is in doubt, and when I'm someplace where there are a lot of forks in the trail, I take screenshots of satellite or map images for what I anticipate would be the hardest sections of the trail to navigate in case GPS fails. (I learned that taking the back roads to ski resorts, saved my ass more than once.)
* Always a spring-assisted knife, gotta be able to open it with one hand, usually not an OTF or switchblade, both for legal reasons and because they're a bit less reliable.
* Only illegal carry I would consider would be something like an asp baton, though they are too damn heavy! I am considering a goose neck mic stand-- still probably illegal, but far lighter, mainly for a dire situation w/ coyotes, (very unlikely to be dangerous unless I were badly injured an unable to haze them properly) or off-leash/stray dogs and mountain lions, but potentially for humans. I should take a gooseneck into the back yard, wear some oven mitts, and try it on a cinderblock or something, this might be a stupid idea. There really are no good weapons for mountain lions except guns, and I don't want to carry firearms (maybe someday, but we're not there yet, and I hope we never will be.)
I'm not carrying bear spray-- it would find a way to go off in my pocket. I know a guy that happened to-- his GUIDE in Alaska had bear spray in a back pack in the overhead rack, it fell out of the pack after a short stop, and my buddy was right in the line of fire.