Add custom field to checkout

Hello,
I need to add a checkbox below where customers choose their shipping method in the checkout. It is to give authority to leave goods unattended. If they tick the box I need that information to be available in the admin email that notifies new orders and on the customer invoice. Any ideas or mods that can do this?
I'm using OC 1.5.6.4 on a clean install.
Thanks.

The shipping methods are already available during checkout. You can go to admin - extension - shipping and enable the required shipping. And they will be available for you.

Yeah sorry I need to add an additional checkbox AFTER where the customer chooses their shipping method. I need a checkbox and if it's ticked I need to state that it's ticked in the admin email that notifies new orders and on the customer invoice.

Anyone have a clue on this one? Adding custom fields to the checkout?

Hi, im looking for a similar function, but in the new user account registration page. i have had no luck yet, and looks like no one responded to your q either. is help on creating additional fields supported on this site?