[niftich]

Here's two good, basic ones:

Access to clean, safe drinking water -- including purifying non-potable water at a variety of scales; and delivery, storage; +1 for overpopulated, or money-poor, or resource-poor, or remote areas.

Access to proper sanitation, including safely handling and treating sewage, much like the point above.

Both of these are unsolved in many places that have cell phones, electricity, refrigeration. While it may seem paradoxical, those comforts were easier to solve than water and sewage.