At the moment, the latest version in stretch is 1.1.4. Sid (unstable) and Jessie (stable) both seem to have it - why doesn't testing?
See https://apt-longview.linode.com/dists/stretch/main/binary-amd64/Packages:
Package: linode-longview
Version: 1.1.4
Architecture: all
Maintainer: Linode Longview Team support@linode.com
Installed-Size: 236
Depends: libjson-perl, libwww-perl, libcrypt-ssleay-perl | liblwp-protocol-https-perl, libio-socket-ssl-perl, libio-socket-inet6-perl, liblog-loglite-perl, libtry-tiny-perl, libdbi-perl, liblinux-distribution-perl, debconf (>= 0.5) | debconf-2.0, perl
Homepage: https://www.linode.com/longview/
Priority: optional
Section: utils
Filename: pool/main/l/linode-longview/linode-longview_1.1.4_all.deb
Size: 25676
SHA256: b080ce8ea866b0243dbc149702cd207a90a8508e4f3355d5f82781e4a895168d
SHA1: e3bcac5d6441aec9ca6064fcce07968b9fdd1b01
MD5sum: 9b2463d8cf480f4a8af9ce8462cdfa56
Description: Longview Monitoring Agent
This agent collects various system wide statistics and
post them to the Longview collection endpoint.