Is there a way within a SmartApp to perform an HTTP PUT/HEAD request? The HTTP methods currently available are wrappers to lower level libs, which is understandable, but is there a means of performing RESTful calls currently? Perhaps on the horizon?
I’ll just brute force it with a proxy if need be! 
Although they are missing from the documentation, there are httpPut methods that will allow you to make PUT requests. The same options are available as for httpPost. Unfortunately HEAD is not there now. We’ll add it and update this thread, and the documentation, when it becomes available. That should be Thursday or Friday of this week.
Awesome. Thank you.
I forgot to ask about arbitrary header support. Any chance that will be available?
bump @bflorian HEAD happen to show up yet?
Yes, the HEAD method is now supported with httpHead.
Great, thanks!