Sitecore's "ultra cool mobile framework" will prove to be a defining moment in their ability to surf the frenzy that is the internet. With an exploding population of netizens hailing from their mobile devices those who can't adapt will undoubtedly pay for it with less engaged, more frustrated users dropping off. Developing a mobile strategy can be a difficult task but Sitecore looks to be poised to help developers handle that task.
The SDK will be built using JQuery and JSON which should give developers a lot to leeway to develop solutions far a variety of mobile devices.
iOS, being as dominant as it is, has an Objective-C library which will support querying items over http/s, caching, security access and even uploading media. That's a lot of power straight out of the gate so anyone who will be using this should have a lot of flexibility in developing a wide array of applications. The library will also support gestures like swiping, navigation and hooking into phone functions with JavaScript, such as adding new contacts, which will quickly gain it popular support. I'm a little surprised to see the use of xslt sublayouts (shudder) but I guess it's a free country.
If, as I imagine a plurality of developers will be, you're going to be supporting more than just iOS, you're still going to have access to the web service that the Objective-C library is using, you'll just have to build your own device specific controls or rely on more generic functionality.
The "Item Web API" will provide JSON results from REST requests and will be the workhorse for your mobile application. The API will be available as an installable module which will enable your system for these mobile queries. Accessing secure content will be handled by using security passed through two HTTP headers. The module will also install specific security settings that will allow you to specify which items can or cannot be accessed through the API. That's a very nice touch as well as the support for RSA encryption of the security credentials if you're not using SSL, although it is recommended that you do so.
The API will, as you would hope, will support language through querystring parameters, although i didn't hear anything about versions, but i may have missed it given the speed we're moving through this talk. While querying items you will also be able to set the "scope" which is what Sitecore is using to describe the related items to return. The parent, self and children will be supported and their order can be set. XPath and Fast queries will be supported through the query string as well which can either be a great asset or a liability but the freedom is yours to choose. Uploading to the media library should prove to be a very valuable tool for enabling user generated content or even developing really slick content editor apps.
The future of mobile enabled Sitecore sites looks bright given the level of commitment already shown in their initial push. Future use will definitely dictate how this will expand but overall I'm really impressed with what they've provided so far.