Doug has his own review of battery-powered signaling devices at http://www.equipped.org/signal.htm#BatteryPoweredAttraction, which details the emergency strobes (e.g. ACR Electronics FireFly series) and the Greatland Rescue Laser Flares. Add in your flashlights, chemical-luminescent lightsticks, and pyrotechnic flares, and that about covers your nighttime visual signaling options.

If anyone knows of something I missed, pipe up.
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“Hiking is just walking where it’s okay to pee. Sometimes old people hike by mistake.” — Demitri Martin