Building a Project Server app
EPMSource have just finished a very nice 4 / 5 part series on how to create an app for Project Online. It even walks through the submission process to the app store.
Here are the direct links to each post
Paul is a an expert SharePoint and Project Server developer and is responsible for designing and implementing custom solutions on client systems using the latest SharePoint and .NET technologies.
Paul has extensive experience with SharePoint systems across all sizes of implementation, ranging from small to large farms and has an excellent understanding of all the elements of SharePoint.