Some time ago, I put together a recipe for watching over recent contents lists from a set of journals listed in a reading list (Mashlib Pipes Tutorial: Reading List Inspired Journal Watchlists). But what if we wanted to maintain a watchlist over content that is published in just open access journals?
Unfortunately, it seems that TicTocs (and the API version (I think), JournalTOCs, don’t include metadata that identifies whether or not a journal is open access. A quick scout around, as well as a request to the twitter lazyweb, turned up a few resources that might contribute to a service that, if nothing else, returns a simplistic “yes/no” response to the query “is the journal with this ISSN an open access journal?”
– a list of journals in TicTocs (CSV);
– a list of open access journals listed in DOAJ (csv);
– SHERPA/RoMEO API (look up open access related metadata for journals?)
So – as a placeholder for myself: think about some sort of hack to annotate and filter TicTocs/JournalTOCs results based on open access licensing conditions
Following a quick bounce around of ideas with @kavubob on Twitter, what else might this be used for? Ranking journals based on extent to which articles cite articles from open access journals, or ones that support some sort of open access publication?
Also – is it easy enough to find citation data at gross level – eg number of citations from one journal to other journals over a period of time? Colour nodes by whether they are OA or note, size/weight of edges between journal nodes to show number of references from one journal to another? Maybe normalise edge weight as percentage of citations from one journal to another and size nodes by number of references/citations?
OUseful.Info, the blog... 
Your original question – about whether a service existed to give open/closed status from the ISSN – was so straightforward I couldn’t believe that we didn’t already have something to do that. You’ve provided some persuasive use-cases above for the API as well. (I recall discussions amongst funders not so long ago about whether an API to this data was of any use.)