My current set up shows a tray icon (in polybar) for dropbox, redshift, firewall, and networks.
When I reboot BSPWM (super+alt+r), I now have two tray icons for redshift and firewall. Rebooting BSPWM again, I now have three tray icons for redshift and firewall.
In launch.sh for polybar, killall -q polybar does not kill the existing redshift-gtk and firewall-applet processes.