External notification of database updates

MS-SQL 2005, C# 2.0

I will have many client databases that will be updated. When they are updated I need to transfer some of that data to a central Server database somewhere on the Internet. Note, schemas do not necessarily match.

Transfering the data (Web Services, Remoting) is not a problem.

What I am looking for is a cool, correct, advisable way, for the client database to notify me of an Insert, Update or Delete. I can then initiate the connection to the Server and 'push' the data (maybe pull some back from the Server too).

Obviously Triggers may be a place to start... But I need to know 'external to the database' that an update has happened or can I send the data from within the SQL Server assembly?

Anyone have any ideas or a technique, maybe something new in SQL Server 2005 (all databases will be 2005), for acheiving this? Just so I don't go down the 'wrong' path...

There are some BLOB's involved (1-2 page PDF's), if that makes a difference.

I envisage that the process transfering the data will be a Windows Service running on each client. The connection may not always be available, so some kind of 'to do' list of outstanding data to be transfered is required.

I'm just starting on this, so any pointers would be great, I'm sure it's all been done before ;)

Thanks

Rob.

One interesting technique to consider would be using triggers and service broker. When an insert, update or delete occurs, send a message via service broker to your central server informing it of the change along with whatever data is necessary to identify it. The central server can then asynchronously receive and process the message.

Dan