You can add any app as dependency and then use forms or modules from that app.
You can create an http_endpoint and call it as any other http API.
You can create an uplink module in your own computer and use it as an API server for your app.
You can create an uplink module in your own computer and use it to call functions defined on your app. Even better, it can access database tables and other app resources directly, without writing any code in the server side.