There is an Extension available to create SOAP operations, which will trigger Workflows from Workflow Designer.
This give you the opportunity to use Workflows from your external Application.

You are also able to transfer parameters and use them in your Workflow.
In the first version there is no option to get a response with information from Vtiger for your Application.
This will implemented within the next update, together with the option to send files.

Download Module file

Install the extension in the Module Manager of VtigerCRM.

This module integrate itself into the Vtiger own SOAP Webservice. You need to have a valid login, which should be done before you send the operation.
To add a new operation, go to “Workflow Designer SOAP” in your CRM Settings and create an operation. You could set a description, choose a workflow to be executed and set a custom operation name after a random prefix.
The operation will always be from request type POST.
All parameter you send to the operation by POST will be available in the Environment variable $env[“parameter”].

The Workflow will be executed without a record by default. So you cannot use any default field variable.
If you submit a parameter crmid, you specify the record, which the Workflow Designer should use for this.

// The SOAP Operation must have this name. You must specify your operation name
$operationName = "81e4a_leadrequest"
// This example will transfer 3 parameter to the workflow
// Login before and store the Session ID in the variable $sessionId
$response = post($endpointUrl."?operation=".$operationName."&sessionName=".$sessionId,
    array(
        'firstname' => 'Stefan',
        'lastname' => 'Warnat',
        'email' => 'email@stefanwarnat.de'
        )
);

Now you could create a workflow which access the variable $env[“parameter”][“firstname”] to get the firstname and similar to access lastname and email. The maximum transportable content depend on your vtiger webserver config. Per default it is set to 2048 KB (2 MB).