I think another interesting development related to this space is GNU Taler[0], which has gotten EU and NLnet grants, and could probably hook into these APIs.
I'm eager to see what the extra funding does for the project. UX, setup, and everything else that relates to integration wasn't something I wanted to work with last time I took a serious look at the project.
Taler is basically just a cover to allow countries to stop printing banknotes and minting coins.
Once banknotes and coins have fallen out of use, there's absolutely nothing in Taler preventing those governments from changing all the rules. They can simply decide to abandon the payer-anonymity as soon as they've migrated people off of banknotes-and-coins. Sorry folks! We had to stop doing blind-signing because AML and terrorists. But that's okay, we'll sign your unblinded tokens instead! And we promise not to store all those token identifiers in some huge surveillance database somewhere. Pinky-swear.
Taler really has very little to do with the internet. It's all about shutting down the presses and mints without provoking riots.