Re: long distance shooting equiptment
You will need an instrument or instruments which measure atmopheric pressure, temperature, and relative humidity for <span style="font-style: italic">long</span> shots. (Humidity may be ignored at 1000 yards or less.)
A Kestrel will also measure wind speed. However, it only measures the wind speed where it is - so having that wind speed is not sufficient to calculate wind effect at long range, because the wind varies.
A Kestrel is useful, though, for learning to estimate wind speed at the shooter's location, which he will often have to do without the Kestrel while actually shooting.
Other than the wind, a Kestrel is not really necessary. Several watches have pressure sensors adequate for atmospheric pressure, and a cheap thermometer is sufficent for temperature.