Now. Create a system service
$ devel-su
# nano -w /etc/systemd/system/prey-agent.service

[Unit]
Description=The Prey daemon.
After=network.target
[Service]
ExecStart=/usr/lib/node_modules/prey/bin/prey
WorkingDirectory=/usr/lib/node_modules/prey
Restart=always
RestartSec=15
User=prey
Environment="TERM=dumb" "USER=prey"
KillMode=process
TimeoutStopSec=20
KillSignal=QUIT
[Install]
WantedBy=multi-user.target

And start it
# systemctl start prey-agent

Enable it on boot
# systemctl enable prey-agent