Twitter offers 'web intents' that are an alternative to OAuth access to their API. Basically, this provides a less feature rich experience, but can still be quite handy. User clicks on 3rd parts websites can create popup windows that check whether the user is logged in to twitter and if they are, allows them to us some Twitter features such as tweeting, retweeting, or following users.
My question is, how could I go about implementing an API like this? Are there tutorials or libraries? I'm not sure what technologie(s) power web intents or where I should start searching.
Thanks.
You can read more about web intents at webintents.org and read the W3C's draft spec. As far as I know, web intents are still somewhat of a new beast on the web and they have not been standardized.
Still, you may want to read this blog which contains a few examples of registering web intents and check out Paul Kinlan's git repo https://github.com/PaulKinlan/WebIntents
Hope that helps you get started.