Connect to web services as part of formula - used for validation, sending data to 3rd party systems etc

As part of a formula it would useful to connect to a web service for validation, sending data to 3rd party systems, retrieving data from 3rd party systems, or even connecting to CRM api using a specified user. Results from web service could be used in formula logic or be persisted to CRM records. See Nintex Workflow for examples of how they have enabled connectivity to web services in SharePoint workflow logic