Setting up Mobile browsing/posting for user sites?

I'm in the process of creating my WPMU niche-driven site. I plan to offer basic blogging/site-building for free and using the Supporter plugin allow for upgrades. One of the things I'd like to offer in my basic feature set is the ability for Mobile Browsing/Posting. I've seen a few threads over the past year on here but nothing concrete, and nothing very current. I'm not sure what the best way to approach this would be. Sure lots of my potential users will have an iPhone but not all of them. I'd venture to say 50% or less, so I don't really want to promote an iPhone only app. Not to mention that you can't Whitelabel the app, so I would have to tell my users to go download a free Wordpress app and that could confuse them. Ideally I would like to offer mobile-phone optimized browsing, but since so many new smart phones out there have a great browser built in, the most important function would be to let the user log in and post/edit their content. What is the best method out there today, that works with Wordpress 3.0 Multi-Site? Thanks.