This year Microsoft released Azure Hybrid Connections and significantly simplified the setup process of hybrid cloud solutions. Before, surfacing surface data from an on-premise SQL server was an arduous task. It may have required developing data migration solutions, mirroring table structures on Azure, and opening firewall ports. Contrast this to the new process: setting up the Azure Hybrid Connection in the Azure Portal, and that only takes a few minutes, then just installing Azure Hybrid Connection Manager on-premise. And you’re good to go.
All communication from Azure Hybrid Connection Manager is securely transferred via outbound ports, and no inbound ports need to be opened in the firewall. Multiple web apps can share a single Azure Hybrid Connection. The connection is framework-agnostic and can be accessed by any conventional web app framework (.Net, PHP, Node.js, etc.).
Azure Hybrid Connections can be used for any cloud solution that makes use of on premise data. My experiences were with setting up an External Content Type for SharePoint (detailed HERE). With your on premise data available on Azure, a number of applications can make use of the data. Some examples might include a custom Office 365 / SharePoint Online add-in, business intelligence solutions, or any other line of business application, so long as it can authenticate to Azure (or you can alternatively write your own authentication).