This extension adds a very simple twig function to fetch and save a remote file and return it's new, path which can then be used in bolt's built in image functions. It works very well with extensions that return data from social media such as my own instagram, facebook and twitter embeds extensions.
Not maintained, will not be updated. If you feel like taking it over, open an issue and I'll transfer the repo. A plugin to integrate foxycart with bolt. See http://www.foxycart.com/ and the github readme for more info.