When it comes to travel, the list of things you "absolutely must have" gets longer and longer with each passing year. My wife and I are in the middle of a year+ trip, and had we done this in the 80s, we would have packed some clothes, a world atlas, a 35mm camera, a Swiss Army knife, and a few books to pass the time.
Today, there is so much gear that is "absolutely necessary" -- from specialized shoes and technical clothing to gadgets of all kinds to a hospital-sized chest of medicine, you'll fill a 90L pack before you know it and still not have enough space for everything.
In our last eight and a half months on the road, we've had the opportunity to put all the items in our bag to the test -- some proved useful and worthy investments, others not so much.
Of everything that did make the cut, the one item we've never second-guessed is our SteriPEN. Why? Because it ensures access to the most important thing for survival: water.
We use our SteriPEN daily. In a little over three minutes, we've got two liters of water that is safe to drink. Using UV light, the SteriPEN destroys any viruses, bacteria, and microbes that might be in the water. It's like a tanning salon in Jersey except that with the SteriPEN, all the housewives die in the first episode. It should be noted here that the SteriPEN will not destroy things like radioactivity, metals, and toxic chemicals.
At around $100 USD, the SteriPEN is capable of purifying 8,000 liters of water over its lifetime (for those at home doing the math, that's a little over a penny per liter). With stories from India, Kenya, China, and elsewhere about fake bottled water, it's reassuring to know that you're getting clean, drinkable water - all from the comfort of your hotel room. There's no need to go on wild goose chase looking for authentic stuff and certainly no need to pay a boatload for overpriced hotel or airport agua to satisfy your thirst. As an added bonus, it's environmentally-friendly too, which is hugely important in SE Asia where the level of litter, especially plastic, is appalling.
Most importantly, the SteriPEN gives us peace of mind - we may freeze, we may starve, we may die in a bus accident, but by god we will be hydrated.