|A situation you probably don't want to experience by Sean MacEntee (CC BY)|
website-poller is a simple Python script you are supposed to attach to your crontab. Set it to poll once per hour or so. If/when a service goes down, a notification will pop up. We support Ubuntu (other Linuxes might work too) and OS X (Growl) at the moment.
It might be nice to grow this into something bigger (get email, stats etc.). Even in its current state the script might be useful for some. Let us know if you have any ideas for further development.