I have developed a C# desktop application which makes HTTPS requests to the customers\' servers (usually Documentum/SharePoint/Alfresco/Nem
Same idea as Mohit's answer, but it can be done with a much simpler code:
//Make initial request for SM to give you some cookies and the authentication URI
RestClient client = new RestClient("http://theResourceDomain/myApp");
client.CookieContainer = new CookieContainer();
IRestResponse response = client.Get(new RestRequest("someProduct/orders"));
//Now add credentials.
client.Authenticator = new HttpBasicAuthenticator("username", "password");
//Get resource from the SiteMinder URI which will redirect back to the API URI upon authentication.
response = client.Get(new RestRequest(response.ResponseUri));