@Subscribe
public void onRender(RenderOverlayEvent.Post event) {
    if (mc.thePlayer.getHeldItem() != null && mc.thePlayer.getHeldItem().getItem() instanceof ItemEnderPearl) {
        EntityEnderPearl enderPearl = new EntityEnderPearl(mc.theWorld, mc.thePlayer);
        BlockPos pos = new BlockPos(enderPearl);
        ScaledResolution resolution = new ScaledResolution(mc);

        if (pos == null || pos == BlockPos.ORIGIN) {
            return;
        }

        if (mc.theWorld.isAirBlock(pos) || !mc.theWorld.canBlockSeeSky(pos)) {
            String warn = "It is dangerous to throw!";
            mc.fontRendererObj.drawStringWithShadow(warn,
                    (resolution.getScaledWidth() - mc.fontRendererObj.getStringWidth(warn)) / 2,
                    resolution.getScaledHeight() - 50, Color.RED.getRGB());
        } else {
            String safe = "You can safely throw.";
            mc.fontRendererObj.drawStringWithShadow(safe,
                    (resolution.getScaledWidth() - mc.fontRendererObj.getStringWidth(safe)) / 2,
                    resolution.getScaledHeight() - 50, Color.GREEN.getRGB());
            }
        }
    }