I check dsipaint.com from my android phone all the time. You have to make sure javascript is enabled on your phone and it even works pretty well even over the cell data connection.
Savant and I check the website from our iPhones when we're out-and-about. Skunkman checks it from his Android. The website was made to mostly work in all mobile devices. Some of the more DSi-specific apps won't work on other platforms, but blogs, bulletin boards, the Library, messaging, the Help Desk, groups, and event much of the Saviis content, all work on smart phones.