Send To isn’t really something you can implement yourself. It’s a combination of application code, plugins, and an inter-application hub.
OneClick plugins take care of the Send To commands. In Softimage, you can use the Plug-in Manager to check out the OneClick plugin (it’s under the Factory location):
In Maya, there’s also a OneClick plugin. It’s not set to auto-load, so if you have problems connecting to Maya, try going into the Maya Plugin Manager and loading OneClick.mll.
The inter-application hub that handles things like finding running instances of an application, starting applications, and passing messages between applications. The inter-application hub uses a set of XML configuration files to describe the applications available on the local system.
You can find these .syncfg files in %PROGRAMDATA%\Autodesk\Synergy.
For supported inter-application workflows, these .syncfg files determine what Send To menu commands are available. For example, Softimage will check for .syncfg files for Maya, 3ds Max, and Mudbox, and if it finds the right versions, add the Send To commands to the File menu.
The .syncfg files are created and destroyed as you install and remove Autodesk applications.
On older versions of Windows where the location of the .syncfg file contains non-ascii characters, you may need to set the SYNHUB_CONFIG_PATH environment variable to specify the location.
IMO, you shouldn’t be messing about with the .syncfg files themselves, despite what this KB article says. For example, you can’t get Mudbox 2012 to send to Softimage 2011 by hacking the .syncfg files…Softimage 2011 just doesn’t support the Mudbox workflow, that was introduced later.