My god, what do we need some of these measurement things for? Let us first enumerate the variables that need (or more specifically can) be measured by a hand/foot held device, in order of utility:
4) Heart Rate
5) Other stuff (
not less useful)
Preceding my feelings on the matter, Alex Hutchinson has posted about new measuring devices on his Sweat Science blog titled Data Overload. The sentence that perhaps sums Alex's feelings best is: "There's no doubt you gain something with more data, but I think you also lose something".