[adri1]

the only thing that occurs to me is an area and rotating object

Code:

CreateDynamicCylinder(Float:x, Float:y, Float:minz, Float:maxz, Float:size, worldid = -1, interiorid = -1, playerid = -1, priority = 0);

Edit:
you can do some like this:
(no tested)

Code:

#define AREA_TYPE_FIXED_PICKUP 1000
forward OnPlayerEnterFixedPickup(playerid, pickupid);
forward OnPlayerLeaveFixedPickup(playerid, pickupid);

Fixed_CreatePickup(model, Float:x, Float:y, Float:z, worldid = -1, interiorid = -1, playerid = -1)
{
	CreateDynamicObject(model, x, y, z, 0.0, 0.0, 0.0, worldid, interiorid, playerid);
	new areaid = CreateDynamicCylinder(x, y, z - 1.0, z + 3.0, 1.0, worldid, interiorid, playerid);
	Streamer_SetIntData(STREAMER_TYPE_AREA, areaid, E_STREAMER_EXTRA_ID, AREA_TYPE_FIXED_PICKUP); 
	return areaid;
}

public OnPlayerEnterDynamicArea(playerid, areaid)
{
	if(Streamer_GetIntData(STREAMER_TYPE_AREA, areaid, E_STREAMER_EXTRA_ID) == AREA_TYPE_FIXED_PICKUP)
	{
		OnPlayerEnterFixedPickup(playerid, areaid);
	}
	return 1;
}

public OnPlayerLeaveDynamicArea(playerid, areaid)
{
	if(Streamer_GetIntData(STREAMER_TYPE_AREA, areaid, E_STREAMER_EXTRA_ID) == AREA_TYPE_FIXED_PICKUP)
	{
		OnPlayerLeaveFixedPickup(playerid, areaid);
	}
	return 1;
}


//inc
public OnPlayerEnterFixedPickup(playerid, pickupid)
{
	new str[45];
	format(str, sizeof str, "OnPlayerEnterFixedPickup, ID: %d", pickupid);
	SendClientMessage(playerid, -1, str);
	return 1;
}

public OnPlayerLeaveFixedPickup(playerid, pickupid)
{
	new str[45];
	format(str, sizeof str, "OnPlayerLeaveFixedPickup, ID: %d", pickupid);
	SendClientMessage(playerid, -1, str);
	return 1;
}

the object has to be rotated to seem like a original pickup