3. Insect repellent (or clothing designed for this purpose)

Bugs can all but ruin a trip. So protection must be taken. Your most effective options are: 1) Lotion or spray repellents containing DEET, and/or 2) Clothing that has been treated with permethrin.

4. Signaling devices, such as a whistle, cell phone, two-way radio, satellite phone, unbreakable signal mirror or flare.

A whistle is a compact, lightweight, and inexpensive way to signal for help. Although a person cannot shout for a long period, he can whistle for extended amounts of time. Moreover, the sharp sound of a whistle travels over longer distances than the human voice, and provides a much more distinct sound. Although environmental factors such as wind, snow, and heavy rain may drown out a voice, the sound of a whistle is clearly distinguishable in the field.

A cell phone, two-way radio, and satellite phone  offers a way of communicating with the outside world should you need assistance. While these are all limited to signals, the sat phone is by far the most reliable of the three.

A signal mirror can be used to signal airplanes or other hikers by reflecting the light from the sun.

5. Emergency Shelter such as a plastic tarp and rope.

The shelter is targeted at day trippers. (Most overnight wilderness travelers already carry a tent or tarp.) The thinking is, if getting lost or injured leaves you stranded in the back country, something is better than nothing if you have to deal with wind or rain or snow. Options include an ultra-light tarp, a bivy sack, an emergency space blanket (which packs small and weighs just ounces), or even a large plastic trash bag.

So…

Of course the trip that you will be taking will determine how much of the essentials are actually needed. A short day hike may only require a few of the items, while a full day of hiking may require more. An overnight trip should encompass all of the essentials.

Some of the items are recommended to keep on your person. Some wear a lanyard around their neck with a few of the items attached to it. As it is though, it is your hike, so hike it how you want, but know that these items are listed for your safety. They will not require much room or add much weight, and if you need them you will be very glad that you have them!