We at Minuscule Technologies have done a solution on Heroku which interfaced with Salesforce and other applications. Following are the high-level details of our solution.
The Hybrid App solution is for an Application that has Web/App solution and we have done using and OAuth 2.0.
The entire application is hosted on Heroku platform and this application fetches the customer data from Salesforce Account Object with HerokuPostgres as its data layer. This application can be integrated with any Salesforce standard/Custom objects bi-directionally.
Build pack used - Java, NodeJS buildpack
Database - HerokuPostgres
Security - OAuth
Technically, the mobile app is a responsive and Hybrid app that works in multiple devices i.e. Android, iOS and Web browsers.