Medical apps: success stories, apps you love, apps that have screwed your health?

Our very own Carl Franzen has a great report up today on the FDA's attempts to regulate medical apps -- loosely defined as those designed to diagnose or treat a health condition.

I've toyed with the idea of downloading some of the apps available (though nothing to treat acne, I swear!); namely a few designed to examine problematic moles (a bit of a skin cancer paranoia over here). I eventually opted not to download any of those, because further research revealed that they were wildly unreliable, and the last thing I wanted was a melanoma alarm being sounded by my iPhone without just cause. I'm wondering if anyone has tried any medical apps, found any that they absolutely love and trust and recommend, or any that proved somewhat disastrous? Of course, I won't trust any of your recommendations as sound medical advice -- nor should anyone -- but curious to know.