SOAP inspection / tampering tools?

["Sebastien Deleersnyder" <sdl () ascure com>]

Hi,
 
Are there any open-source / commercial tools available for inspection /
modification of 
SOAP traffic to perform audits on its security?
I am thinking of a local proxy-like program through which SOAP traffic
is channeled 
by e.g. modifying localhost : redirect traffic destined for target.com
to 127.0.0.1
The tool would allow for changing the SOAP content both in the
request/reply.
I imagine that this only makes sense if the SOAP goes over HTTP, HTTPS
protects against sniffing.
 
I know there are commercial tools available to scan a SOAP server on
vulnerabilities, such as

*       ScanDo (Kavado)
*       AppScan (Sanctum, now WatchFire)

How good are these in finding problems with SOAP calls?
Are there open-source equivalents?
 
Thank you,
 
Kind regards,
 
Sebastien