I just saw the Lotusphere 2011 Mobile Agenda in the itunes app store (released yesterday).
Lotusphere 2011 Mobile Agenda allows you to synchronize your session schedule with Lotusphere 2011 Online. It also allows you to create your session schedule on your device and synchronize it back to the server.There's no hint that it's authorized by IBM - Lotusphere online is linked in the description but it is not online yet.
Logging in is not yet possible and I also did not find any information on the creator's website or blog about the app. So hopefully within the next days we'll learn more about it.
Updates
Of course there's also Ben's LS11 agenda database and the LSMobile iPhone app by the Turtle Partnership (and also the LSMobile HD iPad app).
Also, IntraVision again have a great ls11 web app with session data, searching and planning features. Thanks guys.
As described in the Lotusphere Blog, there's also a mobile access to the Lotusphere Online site.
To login in the iPhone app, use your conference ID, this is the local part of your conference Email address (XXXXXX@lsonline.info) and your confirmation number as password. To get the conference ID, log in to Lotusphere online with a browser using your Name and confirmation number.