Just discovered this forum and have learned a lot in only a few hours browsing. One point that others might find interesting: looking through the threads on water treatment, many people have mentioned using Aquamira but no one has discussed its byproducts.
Aquamira's active ingredient is chlorine dioxide (ClO2), which is widely used in municipal applications at very low concentrations. ClO2 is known to produce potentially harmful byproducts--chlorite and, to a lesser extent, chlorate. Of these chlorite has been shown to be harmful in lab experiements on animals (animenia, neurodevelopmental defects, among others). The EPA, along with the WHO, many European countries, and a few state agencies, regulates chlorite concentrations in drinking water; the EPA level is 1 mg/L.
Aquamira is identical to a product sold in Canada under the name of Pristine. Independent lab tests in Canada show that Aquamira/Pristine's normal dose results in chlorite concentrations in drinking water of up to 7mg/L; its triple dose yields over 15 mg/L. (These tests were conducted using wilderness water from a variety of locations.)
It should be noted that the EPA and other regulations apply to municipal treatment plants, not personal water treatment systems. It should also be noted that lots of people use Aquamira/Pristine and no one is dropping dead. I have seen no indication that a healthy adult using it for a short period of time would suffer any ill effects. Still, in light of the regulations that apply to ClO2-treated water consumed on a regular basis, it seems reasonable to suggest that anyone considering using Pristine for an extended period, or at the double or triple dose, or anyone with an underlying medical condition (including pregnancy or blood disorders) might want to get medical advice specific to their situation. For anyone who is looking for a threshold that is known to be safe, a report commissioned and used by Mountain Equipment Co-op in Canada advises limiting intake of water treated with Pristine/Aquamira to 1.5L/day for no longer than three months, and not using the triple dose. It also advises people with thyroid problems, anemia, or other blood illnesses to use of treatment methods, and says that women who are or are trying to become pregnant should not be exposed to it.
As for the Miox pen, the manufacturer has supplied what appears to be reliable test data demonstrating negligible level of chlorite and chlorate formation.