You should look into WMI - it allows you to query a windows computer and gather all sorts of data; network information, hardware information, resource usage, the list goes on.
I've no experience with Windows Mobile so I'm unsure about whether you can perform WMI queries from it, however if not you could create an ASP.NET based interface which performs the actual WMI calls. You could then visit the ASP.NET page from your mobile device. The other option which operates in a similar fashion is using web services and calling these from your mobile app.
Here is the MSDN section on WMI: http://msdn.microsoft.com/en-us/library/aa394582.aspx
Edit: Actually I went off on a bit of a tangent there; this idea doesn't use the mobile network as asked, my apologies.