Finally got a chance to setup this action from the Workflow iOS app to easily post to my WordPress installation.
You can download my workflow here and tweak it for your needs. It should work for linked posts using post formats and custom fields or for standard posts that don’t pass a link into the Workflow.
With the new Post to WordPress action, the Workflow team has taken parameters for posts, pages, and media that you can post to a WordPress blog and they’ve enabled them as fields in a single action that’s completely under your control.