The Block.io Node.js Sample Code demonstrates how to use Basic Multi-Signature addresses. It provides examples to process transactions, create wallets for users, and use green addresses in cURL, Ruby, PHP, and Python.
Airbitz has utilized its Bitcoin Wallet Plugin API internally and through select partners for a while. Now, the company has released the API to its entire user base. Airbitz expects the API to boost cryptocurrency usage through integrations with everything from marketplaces to gift card vendors.