Possibilities of MS Outlook Web Add-ins on the header/Ribbon in web apps and Independent

I am working with outlook Web-Addins. Addin type is "ItemRead". Now I want some thing unrelated to mails as in i want to have button on header as i see the skype button on the top.

Also we can create Addin on mail compose. I am not sure if this is possible to have separate buttons on header separate from mail section

example in the image of skype button.

I have also tried with Outlook Add-in ModuleExtension but cannot seems to be work as expected in outlook web app.