Fair point, I guess I asked for that one I was wondering under what circumstances he would use it. Outdoors? Is he a first aider covering events?
I was personally looking for one because my 4 year old son has Asthma and his levels gradually declined before needing full treatment. This would give me notice if I needed to get him to a hospital. More importantly, and something overlooked by everyone on this thread, it would tell me that his levels were normal if he was showing similar symptoms that could be caused by something else.