Do humans emit any energy that can be measured through the fingertips?
Put the finger tips of one hand very close to, but not touching, your lips. Do you feel warmth? You are emitting infra red radiation, the same radiation that police helicopters use at night to track burglers, car thieves etc.
Infrared map of a human face
But you do not need to emit anything to operate touchscreens.
Source: Touchscreens
These screens are made from multiple layers of glass. The inner layer conducts electricity and so does the outer layer, so effectively the screen behaves like two electrical conductors separated by an insulator—in other words, a capacitor. When you bring your finger up to the screen, you alter the electrical field by a certain amount that varies according to where your hand is. Capacitive screens can be touched in more than one place at once. Unlike most other types of touchscreen, they don't work if you touch them with a plastic stylus (because the plastic is an insulator and stops your hand from affecting the electric field).
OK, I think that I can interpret this question in this way
"Why do smaller animals seem more active than larger animals (like a rat seeming more active than a dog)?"
Yes, the point that you have noted is quite correct, their metabolic rates are quite fast- (I disagree to the point that this is a question for Biology SE).
Assume that you have a small mouse and a larger animal like an elephant. Now the ratio of Surface Area to the body mass of the mouse will be much larger than that of the elephant, which is fairly obvious
Mouse-$0.875 cm^2g^{-1}$
Elephant (Asian)-$0.0425 cm^2g^{-1}$
(These are estimates I made from data off a few papers, the original values may deviate, but not appreciably)
Naturally, a larger surface area leads to greater loss of heat to the surrounding.
$$\frac{\Delta Q}{\Delta T} \propto A(T_b-T_s)$$
You can see from the above equation, that the heat lost depends on the difference in temperature (known as Newton's law of cooling in physics), and on the surface area of the organism. We take the ratio rather than the total surface area here because a small change in heat will produce a larger change in the body temperature of smaller organisms.
So, in order to maintain their body temperature constant, there is a need for active and constant metabolism. And constant metabolism naturally implies that they must be more active (which means that that they seem to move relatively faster) and need a continuous supply of food to compensate for this process.
But this applies mainly for regulating organisms (i.e. organisms that maintain a constant internal temperature) such as mammals and small birds. You might find a small mammal in the tropics (where $T_b-Ts$ is less) but not in Antarctica, (where $T_b-Ts$ is large).
So, I feel that the point about swatting a fly (or processing information faster, for that matter) is purely an evolutionary incident as opposed to metabolic rates. Lower organisms have a reflexive body i.e. they rely more on reflex signals and the apparent inability to hit a fly is a reflex action- in any case, it is too much to expect information processing in a primitive brain.
Best Answer
The horizontal component of running is believed to be fairly negligible for humans. Some research suggests that the limit isn't strength related at all, but design --- in particular, based solely on power, humans could theoretically run up to almost 40 mph. The issue is two fold: first, our limbs are actually too heavy, for big strength (e.g. climbing in trees) - and weight us down for fast running. The second component is that we're in contact with the ground for far too short a time on each step. For comparison, consider cheetah's - who's long, forward-alternating strides significantly extend contact time.