We have a basic data entry app we want to develop using QT as the development platform. There appears to be Qt Mobility and Qt Web Kit. The goal is to have the app run on as many mobile phone platforms as possible.
What is the recommended approach?
Unfortunately I'm not sure that your approach will work for anything but Qt-based mobile OS platforms (Symbian I believe, and maybe a few others).
Most mobile OS platforms are NOT language-neutral for native applications, so if you want to develop for iPhone you'll need to use Objective-C, Android and BBOS will require Java, etc...
Also, many platforms will require you to use their platform-specific APIs to access hardware, so even if you could build a cross-platform mobile app in C++ using Qt you wouldn't be able to get access to any hardware on the device.
Then again, if it's a web app, why not just develop it for the browser (ie: use standard web technologies)?