Pingdom GIGRIB

Pingdom GIGRIB is a free, unique, distributed uptime monitoring service. GIGRIB users can add websites they want monitored in return for letting their own computers become a part of the GIGRIB monitoring network.

The uptime information for the thousands of websites that have been added by GIGRIB users is public and searchable. Each GIGRIB user can add up to 10 different websites for monitoring. The downtimes of all added sites can be seen on uptime.pingdom.com.
When you install the GIGRIB client, your computer becomes one of the many “test nodes” that report uptime for multiple websites to a central location. Every website monitored by the GIGRIB network will always be tested from several of these test nodes.

For every hour of work your GIGRIB client does for the Pingdom GIGRIB network, you get an additional five hours of uptime checks for the websites you yourself have added. You can accumulate up to 30 days of monitoring this way, ideal if you go on a vacation and will have your computer turned off for days.