Depending on

how critical your site is and
how often you access it personally (eg: daily?),
how worried you are about your host,

you may want to look at having it formally monitored:
There are so many sites out there offering this service with a variety of features:

http://www.siteuptime.com/
http://site24×7.com
http://www.alertra.com/
http://pingdom.com/