Is it possible to programmatically open Safari and/or mobile Safari in Reader mode?
The reader functionality appears to be derived, in part, from the Readability project. It might be worth reading up on a few of the resources out there which look at reader in more detail. Some good starting points, and links to other resources:
With regards manipulating Safari / reader, I'm not aware of any relevant API offered by Apple, and I'd be surprised if they offered specific code to put a site in reader mode. After all, the option to invoke this functionality should really be user-initiated if one is going by standard human interface guidelines.