Do I want apps that install instantly from the page, can't reach into my photos or contacts, and that even I can develop for all platforms without learning OS-s

Do I want apps that install instantly from the page, can't reach into my photos or contacts, and that even I can develop for all platforms without learning OS-specific APIs? Yes. I use some already, though a lot of apps today are mobile-friendly versions of websites, so I just use the website (e.g. Twitter, YouTube, FreshRSS, ...)