via blue, thx :p
apt-get install debian-keyring
gpg --no-default-keyring --keyring=/usr/share/keyrings/debian-keyring.gpg \
--export bernat@debian.org | sudo apt-key add -
tee /etc/apt/sources.list.d/haproxy.list <<EOF
deb http://haproxy.debian.net wheezy-backports main
EOF
apt-get update
aptitude upgrade haproxy