Likes: Tiny, deadly, convenient and effective. Far smaller than other purifiers, it's great for hiking and overseas travel. Easy three-step operation: set water volume and activate flashing lights by pushing a button; submerge lamp and sensor in water inside any wide-mouth container with a 1.75-inch opening; stir until LED indicator turns green, signaling that purification is complete. The UV lamp provides 8,000 treatments — a lifetime for most people. Serves as a backup flashlight when not in purify mode. Doesn't require filter cartridges, as pump- and gravity-fed systems do. Includes a neoprene travel case with a Velcro strap.
Dislikes: None. Requires non-rechargeable CR123 camera batteries, which last for 100 treatments. (An Opti with a Solar Charging case and rechargeable batteries is $149.95.)
Price: $89.95. (888) SteriPEN; http://www.steripen.com.
Charging on the go
Neon Green Backpack: Medium-sized day pack incorporating a thin, flexible, 14-by-10-inch panel of solar cells, a rechargeable battery and a USB port for charging your mobile devices.
Likes: Practical. Located on a zippered, detachable unit that houses the battery, the solar panel can be removed and attached to a standard backpack. When four blue lights and one red one on the battery are lighted, it's fully charged. You can charge your cellphone or camera at any time by connecting it to the battery's USB port.
Dislikes: Charging is slow. I needed about 8 to 10 hours of sunlight to charge the battery, which has limited capacity. A half-charged Neon battery restored about one-third of my cellphone's charge in one hour while becoming completely drained itself. You can't charge the battery and an electronic device at the same time. Not a hard-core backpack for heavy loads.
Price: $199. http://www.goneongreen.com.
Leki Micro Stick: Fixed-length featherweight three-section aluminum pole held together by shock cords, like a tent pole.
Likes: Compact and light. Extending the pole to full length and locking it with the Speedlock clamp holds the three pieces together. Available in three sizes (43.3, 47.2 and 51 inches) that weigh 8.0, 8.8 and 9.6 ounces and pack down to 13.5, 15.5 and 17.5 inches, respectively.
Dislikes: Cannot be adjusted to shorter lengths. It's a bit heavier than carbon poles and has no suspension, like some other Leki models.
Price: $149.95 (800) 255-9982; http://www.leki.com.
Keep track, get back
Bushnell BackTrack GPS D-Tour: Cellphone-sized, 6-ounce device that records your route, guides you back home, then downloads the adventure to a PC with enclosed USB cable.
Likes: Safe, simple and light enough not to bother a hiker or runner. Just press the button with the hiker icon to log elapsed distance and speed, then push again to stop recording. To backtrack, push the other button and follow the arrows. The D-Tour stores up to five locations, then provides simple distance and direction instructions for each waypoint. Includes a digital compass with latitude and longitude readings, plus time, temperature and altitude. A computer app overlays the route on Google Maps, telling you how far and fast you ran or hiked and letting you see your speed at any point on the route. Includes a back-lighted display for night viewing and a carabiner loop for lashing to clothing or a pack
Price: $119. (800) 423-3537; http://www.backtrackgps.com.
Wallack is the co-author of "Barefoot Running Step by Step." email@example.com