Other posters are right, that services should really be started as services. I have a piece of code which turns any basic foreground app into a daemon, with logging and auto-restarts and it's great for node.js and similar. Time being available I'd like to share this online sometime.

As for your specific situation, I do something similar but with screen not tmux. A cron job with @reboot, and then a screenrc file starts each terminal with the appropriate application. This is good for systems such as realtime audio processors which have a live display, which straddle the line a little between a daemon and interactive application.