An armchair quarterback is someone who offers advice or an opinion on something in which they have no expertize or involvement. An armchair general is a person who sits in a chair behind a computer and leads people or at least attempts to, instead of doing something themselves. Such a person usually complains about government, organization, military, political, or religious events through blogs, forums, and social networking sites.
So, basically any role fulfilled from the armchair, i.e superficially, without real knowledge, expertize or involvement can be (disapprovingly/mockingly) termed an armchair (something). I have come across armchair strategist, armchair conscience keeper, armchair critic, armchair psychologist, armchair GM, armchair adventurer, and even armchair traveler.
See how the expression has been used here:
However, an armchair traveler has a slightly different connotation. It is not used as pejoratively as most of the others. Armchair travelers are ones who do not physically leave their homes but experience travel by reading books and watching videos on different countries, cultures, and customs, and through wishful thinking. This website claims to offer sights and sounds from all over the globe, for armchair tourists: http://armchairtourist.com/
Another expression with similar meaning: A backseat driver.