I have done a couple of sections of 508 reviews, but I do not accept what I say as a last word or legal opinion.
Section 508 is commonly used in government contracts and is part of the procurement process. If your application does not fully meet the requirements of 508, this does not mean that you canβt get a contract, it just means that you can lose if someone has an application that is more compatible, and then yours with the same common set of functions and ease of use.
Regarding 508 compliance on a mobile device, the VPAT, which is the form you need to fill out, does not specifically mention smartphones. Take a look at http://www.itic.org/policy/accessibility View the current VPAT. If I had to fill out a VPAT, I would focus on βSection 1194.21, Software Applications and Operating Systems,β since you are writing an application for what is basically a computer with assistive technology.
I am a completely blind iPhone user and from my personal experience with the availability of Apple applications, as well as many third-party applications, I would say that creating an application compatible with 508 or very close is doable.
Android is a completely different story. I have no experience with Android, but do it at different Android levels, different hardware and settings from device manufacturers, which can negatively affect the availability, which you cannot guarantee that your application will be available. The best thing you can do is try to find a phone with good availability, develop on this phone, and in VPAT make it clear that you tested on only one specific hardware device so that your results change. With Apple, it's safe to say that if the application is available on iOS 4.0, it will be available on iPhone 3GS, iPhone 4, iPad and iPod touch, as they control the operating system and hardware. I understand that the accessibility API for Android is more limited than apples, so this is something else to take into account.
For information on making iPhone apps available other than apple documentation, see this
For an overview of the general availability of Android, see this . Pay attention to the choice of the phone section for more detailed information about the fragmentation problem that I mentioned earlier.
For a developer introduction to write affordable Android apps, see this