Following discussion in #810506 and the ACK by the backports team, I've uploaded linux-grsec package (version 4.4.7-1+grsec201604152208+1~bpo8+1) to jessie-backports, and it has been ACCEPTED this morning (along with linux-grsec-base support package). So if you have a Jessie install with backports enabled, linux-grsec should be one apt call away:

apt install -t jessie-backports linux-image-grsec-amd64

4.4.8 should follow soon

.