The problem with medical devices in general falls under two categories: research and developement, and liability. The technology exists for a $75 palm pilot attachment which will do a full 12 lead; the problem is the FDA, and the fact that you have to support a billion(s)-dollar corporation until it's approved.
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Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein