Heat is quite danger for any system, PC, laptop, headless server, Media server...etc. Beside the best cooling system you can build, monitoring system to know how it is going is also a need.
Psensor is a good choice to monitor your system temperature.
It is a hardware temperature monitoring tool, was updated recently with an option to display the temperature on the panel (next to its AppIndicator icon), along with other improvements and bug fixes. I'd like to have it, especially on old pc, laptop that have long service cooling system.
sudo apt-get install lm-sensors hddtemp sudo sensors-detect sudo service kmod start
sudo add-apt-repository ppa:jfi/psensor-unstable sudo apt-get update sudo apt-get install psensor