Android app for existing point of sale system

We are looking for excellent android developers to create an app for our point of sale system. We already have a point of sale system developed in PHP/Zend framework. At present, it works online and offline on any browser and has responsive web interface. Now, we want to develop an android app for our tablet users. Current system works perfectly on tablet as well, however we need a native android app to further enhance the user experience. This app will just be the interface to run the sales screen of our comprehensive point of sale system. Attached is the screenshot of sales screen. Android app will just have one screen (exactly similar to the attached sales screen) and this app should be able to work online as well as offline. In online mode, it should sync all the data with our servers. This system will be quite similar to the following apps: 1. [login to view URL] 2. [login to view URL] Necessary conditions: 1. Apply only if you have a already created similar software/app before. Share the links of relevant android app that you have created 2. NDA needs to signed and legally enforceable. We will have exclusive right to the app and you need to provide complete source code & related material 3. Most important of all , NO MILESTONE PAYMENT. You need to deliver the complete project, then we'll make the full payment. 4. Budget is not a constraint for the right candidate. Faster you deliver, faster we pay. Apply only if you satisfy above mentioned conditions. Let me know in case of any questions and feel free to suggest ideas to further enhance the UI/UX