To use debmon with squeeze you need to add the following lines to your sources.list or to a file in /etc/apt/sources.list.d/.

deb http://backports.debian.org/debian-backports squeeze-backports main
deb https://debmon.org/debmon debmon-squeeze main

Afterwards you can install packages with the following commands:

$ apt-get update
$ apt-get install 

To use debmon with wheezy you need to add the following line to your sources.list or to a file in /etc/apt/sources.list.d/.

deb https://debmon.org/debmon debmon-wheezy main

Afterwards you can install packages with the following commands:

$ apt-get update
$ apt-get install 

Unless you import the archive key apt will complain about the repository. To get rid of this warning you have two options. You can either install the debmon-keyring-package or install the key by hand:

curl https://debmon.org/debmon/repo.key 2>/dev/null |apt-key add - 
OK

The key is signed with the key BC7D020A (Alexander Wirt ) if you want to check to trustpath to a Debian Developer.

gpg --list-sig 29D662D2
pub   2048R/29D662D2 2012-10-03
uid                  debmon.org (debmon.org repository signing key) 
sig 3        29D662D2 2012-10-03  debmon.org (debmon.org repository signing key) 
sig          BC7D020A 2012-10-09  Alexander Wirt 
sub   2048R/575BA6B9 2012-10-03
sig          29D662D2 2012-10-03  debmon.org (debmon.org repository signing key)