The most basic monitoring is having the system mailserver send you an email when something is wrong. I use exim and qpopper, which sends mail to root and by using a mail alias it's delivered to one of the users on the server. I can than read that mail from my desktop with any emailclient in my inbox.
Sms sounds fancy, I would like to know that too

Still, I sometimes leave a console running tailing some logfiles just to see what's going on (good or bad).