GenealogyAgent.com <http://genealogyagent.com/> can actually search genealogy sites for you. It will monitor several genealogy sites based on information you give it about your ancestor, and when new data is found, will send you email reports.
The agent does more than just scour genealogy sites for information on your ancestor, it keeps track once information is found and alerts you if that information is changed (updated). It is a bit like Goggle Alerts, but with a bit more focus on genealogy and a lot more discrimination in terms of changing data.
This is a fee service, but like all services, if you need it, it's worth it.