Bypass GPG signature checks only for a single repository

You can set options in your sources.list:

deb [trusted=yes] http://localmachine/debian wheezy main

The trusted option is what turns off the GPG check. See man 5 sources.list for details.

Note: this was added in apt 0.8.16~exp3. So it's in wheezy (and of course jessie), but not squeeze.

To make sure that you see a warning while using an insecure repository, better use allow-insecure=yes instead like below

deb [ allow-insecure=yes ] ...