stock fGetPlayerSpeed(player, bool:return_km=true)//by Frog163    
{    
       new Float:x, Float:y, Float:z;    
       if(IsPlayerInAnyVehicle(player))    
       {    
           new veh = GetPlayerVehicleID(player);    
           GetVehicleVelocity(veh, x, y, z);    
       }else GetPlayerVelocity(player, x, y, z);    
       return return_km?floatround(floatsqroot(x*x+y*y+z*z)*195):floatround(floatsqroot(x*x+y*y+z*z)*121);    
}

public OnPlayerConnect(playerid)    
{    
       SetTimerEx("Timer", 50, true, "i", playerid);    
       return 1;    
}    

forward Timer(player);    
public Timer(player)    
{    
       if(!IsPlayerInAnyVehicle(player)) return true;    
       new str[20];    
       format(str, 20, "%d kmh", fGetPlayerSpeed(player));//для км/ч можно не указывать 2-ой параметр    
       SendClientMessage(player, 0xFF00FFFF, str);    
       format(str, 20, "%d mph", fGetPlayerSpeed(player, false));//чтобы узнать мили во второй параметр пишем false    
       SendClientMessage(player, 0xFF0000FF, str);    
       return true;    
}