Attendance in Cloud - multiplatform mobile app

We have server-side ready for our cloud Employee Attendance system with JSON REST api. Now we need multiplatform client-application that would serve as a simple client. App should run on Android, iPhone, iPad, Windows Mobile and BlackBerry. It should be able to let user login, insert own attendance (08:00 Work-start, ...) including optional GPS position, photo from camera or file from device as attachment. Entered data are stored in mobile device memory. If mobile device is online, data are sent directly to our cloud server and deleted from device. If offline, data should be sent to server later, after connection is restored. Depending on user's permission (determined on login), app should be able to browse daily and monthly attendance summaries of own or also of other employees in the system. There should be also a shift-calendar, so employee can see own plan of shifts. After instalation, mobile device has to be "paired" with company's account in our cloud app. That is done by entering company's login + PIN or using QR code generated in cloud-app web-gui. Once paired, this screen is not shown anymore. Therefore we need to read QR codes in this mobile app! On first run, there is several slides with "wizard". Texts in app should be easily translatable to other languages and not "hardcoded".