The following simple items can help rescuers find you in the event of a backcountry emergency.
A whistle. Shouts for help can only be heard a few hundred yards away, at best. The piercing sound of a loud whistle carries more than a mile away. What’s more, you can blow a whistle in regular bursts for hours—long after your voice gives out from shouting. A series of three short blasts is the universal distress signal.
Bright colors. Carry or wear something that stands out from the landscape to increase your visibility, especially in the event of an aerial search. Orange, red, and yellow hues work well, especially in winter. Space blankets, tent rain flies, and contractor trash bags often come in highly visible colors.
A shared itinerary. Always tell someone where you are going and when you expect to return.
A cell phone. You should never rely on a cell phone—batteries die and coverage in the backcountry is often unreliable or nonexistent—but it can be a potential first line of help if you can get reception. Keep your phone powered off when not in use, seek higher ground for a better signal, and if the signal is too weak to place a call, send text messages to increase the likelihood that an SOS will go through.