Not the most widespread platform, but there are applications that let you create windows phone apps without knowing how to code. There are a few options for Android as well, but I haven't tried those: http://andromo.com/ and http://www.androidcreator.com/
Easiest would be in php. If you know android programming use Android Studio: http://developer.android.com/sdk/index.html
You can use App Inventor too: Version 1 http://appinventor.mit.edu/explore/ or 2 http://ai2.appinventor.mit.edu/. Check before start deploying as they seem to have differences.
You can take a look at BPM tools also, where you get a browser based screens which work seamlessly on mobile as well as PC's. Some open source tools are Joget, Processmaker et all, else some paid versions are hosted or on-premise like integrify, kissflow et all.
In my opinion Issue Tracking Products (or Incident Management Systems) could be quite suitable for the purpose. There are free packages of this class. The enterprise CRM system can also be used the manage customer complaints.