Yes, the excellent WebOS is defunct, and it will never be the mainstream player as, at least technically, it deserved. For all of us developing for the mobile world that don’t have the time or budget to develop natively in all the mainstream platforms, its one less player to target. Myself, personally, am deciding/evaluating available options for true cross-platform development targeting iOS, Android, Blackberry and Windows Phone 7.

My requirements are:

• Native UI components must be used – maintaining the native look and feel for each platform is important (PhoneGap is out of the picture because of this);
• The same code base (or at least most of it) must be used in all platforms;
• The UI must scale well between Phone and Tablet formats and screen densities (DPI);
• The application must perform smoothly, speedwise, even in lower end devices;
• Some access to the device’s hardware: GPS, sensors, camera.

I have found some platforms so far:

• Titanium Mobile: this is my current number one, but i don’t think Windows Phone 7 will be supported. Plus, the Android implementation is a bit clumsy: the JavaScript core is not interpreted by the OS, so a java JS interpreter is included- this makes the application big and slow. In iOS this problem does not exist, as the system’s javascript interpreter is used. On the plus side, native UI components are supported and a very nice, Eclipse based, IDE is provided;
• PhoneGap: this one also uses JavaScript, but is completely HTML/JS based: the application runs inside a WebView, and has no bindings to native UI components, it relies on third-party JS libraries to build the UI, such as Sencha Touch or jQuery Mobile. It’s a browser on steroids basically, and doesn’t float my boat.
• RhoMobile: haven’t tested or reviewed this one yet, opinions anyone?

So, i need your opinion about these or other development tools: are they any good? Have you used them in a project? Comment below.