Any index may be created, via the appropriate calculations, for a targeted application.
This particular power index has been accepted in T&F throwing circles for sometime and, as a result, I find it useful for comparing the physical preparation of my athletes to that of elite throwers; if only from the standpoint of their power output via hip/knee extension in the vertical plane.
http://members.ozemail.com.au/~b.wagner/Throw/HammerCalc/Powerindex.html