Port existing Android app to iOS (iPhone)

We need to port existing Android app to iOS (Swift, iPhone 5 and up). It's a business app using client-server architecture, where server part is done using Windows Communication Foundation (WCF). The server part is already working with Android app and not going to be altered. The app has 4 screens with basic elements, mainly buttons. Here is a brief description of what an existing app is doing: It periodically checks with the server for new configuration, which comes as XML string. Depending from that configuration, it forms the main screen, which consists of buttons and has vertical orientation. Configuration describes the height of the button, text, image and mp3 file to play on press. There are some additional pre-defined functions that may or may not be called when the button is pressed - make a picture, send gps coordinates and calling a particular function in web service. Another screen is the address book. Contents, such as name, phone and e-mail, are given in configuration. For each name there are two buttons, to send either call or send message through the web service or SMS. It might be that iOS application won't be able to send SMS message, although that's the function of the Android app. The functions will be especially important and require your expertise: • Backward and forward timer, which is working regardless of whether the app is active. The timer length is about 15 minutes for backwards one, after which it should be able to vibrate once. • The change of configuration must be reflected asap, but if any button is active then it should be postponed until no button is active. • Application should regularly check for new messages on server (run WCF function) regardless of whether the app is active. • Application will be installed on business phones, hence security restrictions are not important, if the platform allows. Unlike the Android app, the iOS app should be good looking. In other words, UI is more important here, despite the same functionality. I expect this app to take up to 30 days of your time. The budget is approximate, suggestions are welcome.