Being sighted myself and not having worked too closely on anything that has ever been audited for accessibility or heavily accessed by blind users, I don't think my answer will be terribly thorough. My first instinct however is to say that some kind of dynamic web server architecture that generates HTML like C#, PHP or ColdFusion is going to fit your description of handling most of the layout for you without requiring that you specify control positions in pixels. There certainly is the availability to specify control positions in pixels via CSS, but it's not required. And I know HTML also has well defined standards for accessibility, whereas I'm not sure what the status is on accessibility standards with other kinds of software.
