So when Windows Mobile 6.5 hits what will developers get? Well apparently it will be easier for developers to access writing apps which consume cloud services while up until now developers only had two options for creating apps for Windows based mobile phones.
With Windows 6.5 they have added “Windows Mobile Widgets” a new option for developers. “Windows Mobile Widgets” can be thought of as a rich internet app or a “Portable chunk of the web.”
Windows Mobile Widget is a rich Internet app which allows them to look and feel as a normal standalone app does. For this new platform there will also be the latest draft of W3C standard for mobile widget apps with basic native support for Window.XMLhttpRequest and transparent PNGs
Source — msdn