Web Services Monitoring

I am investigating on existing open source products to monitor web services, at a minimum to detect if there are changes in their WSDL, being able to navigate in their data type schemas, ping them to check if they are available...

given the high number of Web Services we are going to deal with, it's worth to have some sort of registry.

I am testing this

Hyperic http://www.hyperic.com/  this seems to be excellent, but it seems not specific to Web Service (still investigating)

Membrane http://www.membrane-soa.org/

and of course more in general NAGIOS for IT infrastructure monitoring:   http://www.nagios.org/


I know of Amberpoint, which seems to be quite good, but it's not opensource.



Please shout if you have already done some investigation on this topic


thanks