I needed a quick way to test a few things on a webapp running locally (on my Linux box) from another machine running Mac OSX.
Quick and easy way (although insecure, make sure you only do this on a private LAN) was to use socat.
Install on Archlinux (server):
sudo pacman -S socat
Install on the MacOSX client via homebrew:
brew install socat
Proxy local connection to the LAN (on the server; assuming the webapp runs locally on port 5000):
socat tcp-listen:8000,fork tcp:localhost:5000
Proxy remote connection to localhost (so we can access it with the benefits of "local" apps in a browser; otherwise, we would have to have the app served via HTTPS to, eg. use location services):
socat tcp-listen:5000,fork,bind=127.0.0.1 tcp:192.168.x.x:8000
..where, of course, 192.168.x.x is the IP of the server machine.
Now, you can just visit http://localhost:5000 from the client.