Sharepoint - Is it possible to launch local application (exe) from Ribbon control?
Create a reg file and install on the user's computer (this might be too restrictive for you though)
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\yourprotocol]
"EditFlags"=dword:00000002
"URL Protocol"=""
@="URL:yourprotocol protocol"
[HKEY_CLASSES_ROOT\yourprotocol\shell]
[HKEY_CLASSES_ROOT\yourprotocol\shell\open]
[HKEY_CLASSES_ROOT\yourprotocol\shell\open\command]
@="C:\\yourscript.exe %1"
Then output your protocol links in your URLAction
<CommandUIHandlers>
<CommandUIHandler
Command="Ribbon.Extended.SPC3.CreateListProfileField"
CommandAction="yourprotocol://?arg1=1&arg2=2" />
</CommandUIHandlers>
http://msdn.microsoft.com/en-us/library/aa767914%28v=vs.85%29.aspx
You might be able to cut out the silverlight bit altogether and use WScript/COM from Javascript. User's browsers will need to be set up correctly though to allow that.
Example
http://www.olavaukan.com/tag/wscript/