Opportunistic apt sources?

[Richard Hartmann <richih.mailinglist@gmail.com>]

Hi all,

I was wondering if there was any such thing as an opportunistic apt
source.

By opportunistic, I mean that I want to be able to define repositories
that have no Packages.gz of their own and might or might not be
available at any given time.
If I try to install foo, I would love to have a way to try a few other
sources before falling back to the proper servers configured.

I.e. when I am at home, my laptop would access my main desktop
box which is usually up to date.
If I am at work, my laptop would use the company's debproxy.
If I am somewhere else, I would use a proper mirror.

Obviously, there would need to be some sort of mechanism to
discard packages which can not be verified to guard against MITM.


Does anything like the above exist?


Thanks,
Richard