You want to design your application with a set of API's to that you can connect into other things easier rather than building one off integration. Imagine if you bought a TV and a DVD player and now you had design and develop a cable yourself to connect them because one or even both of them didn't use HDMI, RCA or other standard connectors. How much cost would there be in your building that cable in your toolshed?

Unfortunately just because you do build APIs doesn't mean you can easily connect to everything. That's where the middleman comes in. There are companies like Celigo, Mulesoft which got bought my Salesforce and others that build connectors into a lot of applications. That means if you can connect to the middleware, you can connect into other applications easier. Still work to do. Not as easy as plugging in your toaster, but easier than building everything yourself. Ideally, you would drop your application inside their so it looks and feels the same. So you would have a button, dropdown menu or whatever inside Dynamics or Outlook to bring up notifiCRM, but behind the scenes your data, contacts, etc are all sync'd for you.

I forgot to mention in my other post, integration into Outlook is so important for your contact list as well.