[mark254]

Try http://xpra.org/ - that's a "gnu screen" for X11, but bandwidth-optimized, can also relay USB, audio, ...

Just to give you an idea: I used it for forwarding a Firefox window across an UMTS connection when sitting in a train. (Long story: 32bit Java required to remote desktop into a client's environment across the Atlantic, ugh.)

[BLKNSLVR]

I have tried xpra, and it was my go-to option until I tried NoMachine. I did try just forwarding windows, Firefox it was too, but there was some(times) frustrating delays.

I may re-visit, however, as the delays could have been network/environment issues rather than the technology.