Up until now I only had a look at accessing Groove Web Services (GWS) locally (SOAP-client on same device as Groove Workspace). The Groove Access Point can be used to access GWS remotely. Although remote access is only available in 'Preview Mode' in the current release of Groove (2.5a), it gives a good insight in what will be possible.
Check out this page to see 'remote access' in action. I use PHP and NuSOAP to do some simple Read-operations on a remote Groove-account. So how does it work? First one has to register with the Access Point, so the AP knows to which device to forward the request. This is done by the 'gnslnsreg' utility which can be found in de Web Services GDK (gnslnsreg has dependencies on the MS SOAP ToolKit 2.0 SP2 and MSXML3.0, so make sure you've got those installed). After registering it's simple: make the call to http://webservices.groove.net as you would do with a local request.