how to display that a term is inside emacs

[henry atting]

On X I have no window decoration, emacs starts without mode-line, menu,
toolbar. One of the things I use emacs is as terminal emulator
(multi-term). So far, so good.
At times I open up rxvt-unicode as terminal emulator beside emacs. Both
look rather similar, no decoration, same background- same foreground
color. 

Is there a way to add something informative to the prompt (like the file
manager ranger does) or display somewhere else something like
`inside_emacs' for instance to indicate that this terminal is inside
emacs?

henry