Blog server went down for a while

As hopefully some of you noticed, my blog server went down for at least 24 hours.  Not sure why, but since it was a SUnday and I don’t post too often on Sunday I didn’t notice until I was at work today and tried to make a few posts before starting work.  I remember hearing about some service that checks whether your site is up and send an email when it is not available.  Not sure what I could have done from work today, but if I would have received a notice yesterday I could have fixed it.
Whether to move to a commercial host is something I play with now and again.  I have a wordpress account (signed it up when I need an WP API Key to use the Akismet spam service) that I may start using.  ANyone have any thoughts on the difference in using wp.com vs. running your own instance of wp?