Not to mention it's nice to know you have another professional pilot on board to use as an option should the unfortunate need arise. Jumpseaters have been used in the past and will be used in the future. Part of using all available resources...

When you sign for the Jumpseat you are accepting being a part of the crew. That alone warrants talking to the Captain. If he is busy and brushes you away to your seat in the back that's fine but he will still remember seeing you and know you are there.