On the one hand, we can crack down hard on anyone who tries to even hint at some medical or safety purpose for a particular app. On the other we can be wild and free-booting and allow people into precisely the sort of trap that the poster outlines.
These apps may well be better than nothing (though they are not tested in any meaningful sense, nor are they compliant in any meaningful sense), but to the extent that they give a false sense of security, they are dangerous.
Personally, I lean towards crystal clear disclosure, and, in Canada, and restrictions on marketing. I do not favour an outright ban, since I could see that as having unpleasant consequences.
Look forward ten years. Suppose my smartphone has a ~90% reliable software and sensor package to tell me if I'm suffering from a heart attack. Suppose also that I'm part of a demographic group that by gender, age, fitness, weight, diet is highly unlikely to be suffering one. (There have been cases before where software has successfully diagnosed heart attacks in situations where physicians didn't believe it -- consider the case of psychologist Helen Smith a fit 37 year old woman who came close to dying since humans didn't believe she could be having a heart attack).
It would not make rational sense in that case for me to purchase a $1000 bespoke medical device to monitor me, but a $5 app might make sense even if it wasn't as reliable.
Similarly if I ski only occasionally and in areas highly unlikely to suffer an avalanche, it might make sense for me to not purchase a transceiver. (For those who say they'd spend anything to protect their lives, even on extraordinary low probability, I suspect you may have some irrational optimizations in your life.)
Offering consumers informed choice seems key; if they are marketing their apps as the equivalent of Avalanche transceivers, that clearly is not informed choice.
Similarly, I'd pressure Google and Apple and Blackberry to come up with a common standard for fine grid device location that these apps could use.
The OP raises some interesting points; I still come down somewhat on the libertarian side of things.