My current solution is to use two socks servers on the phone. It might seem strange to need two, but this allows routing depending on source address and destination address. The first SOCKs server is dante which routes all "normal" traffic directly to the chosen Internet connection on the phone. Traffic which wants to go to selected addresses on my Intranet is instead forwarded to a second socks proxy on the phone. This second socks proxy is implemented with ssh "DynamicForward" to send traffic over the SSH link to the Intranet.
The glory here is that Internet traffic goes directly, and Intranet traffic is sent over an encrypted pipe to the Intranet. If on the other hand I connect to any router on the Intranet, the phone gets a local IP address and dante is instructed to "route" traffic from that local address directly to the target instead of to the second local ssh socks server. Thus I don't have to concern myself with the details of which side of firewalls I am on, the phone automatically does that for me and chooses the most efficient route for packets.
Having a phone that runs so much like a proper Linux distro makes this sort of thing fairly easy to get going. No need for funky NDKs, NDAs, or TLAs.
If you want to play around with this stuff I have dante debs in my repo:
Using non privlidged ports on the phone means you can run danted as a normal user. I have an icon on the n9 home screen that makes sure dante is running instead of using init.d at the moment. Also, an icon that runs a bash encapsulated with tsocks can be handy for tinkering:
Desktop file segment:
Exec=meego-terminal -n -e /bin/sh /home/user/bin/create-tsocks-env
$ cat /home/user/bin/create-tsocks-env
Using a similar style Exec in a desktop file one can start the SSH client in "-N" mode and use the passphrase to connect and setup an SSH connection with a socks server on the phone. It is quick and dirty without shiny QML interfaces, but it works^TM.