How to connect 3rd party tcp/ip device to Nexus7 I have a wired tcp/ip based device that I need to access from an android app running on a rooted nexus 7.

There is only one hard-requirement1. The tablet's primary internet connectivity must NOT be affected (3g and wifi).
and a couple of preferences...
 2. Preferably the device would be accessed wirelessly.
3. Preferably this would be accomplished without additional hardware physically attached to the tablet.

The options as I currently see them...


Bluetooth

obviously this would require some sort of ethernet to bluetooth gateway.  I would rather not pay more than the price of the table for an industrial device which has significantly more capability than what I would need. So does a consumer version of this even exist? If it does would the resulting bluetooth connection on the tablet interfere with the 3g/wifi internet connectivity or is that something I can workaround with special routing rules or just coding the app to use bluetooth rather than sockets?
Wifi

Is there a way to accomplish this while still meeting requirement #1?  Maybe attaching a USB dongle via the tablet OTG connection and running two simultaneous wifi connections with special routing rules?
Wired

USB RJ45 dongle via tablet OTG connection?  This is similar and possibly simpler than the wifi option yet has the same potential issues regarding having two network connections active concurrently.  


Any thoughts, suggestions, creative solutions?
The obvious solution would be to use a device that has both ethernet and Wi-Fi as a router or a bridge. If it joins the same Wi-Fi network that the Nexus 7 is on, then the Nexus 7 will be able to make a connection through the router/bridge to your mystery device, while also talking to the Internet through the same Wi-Fi network. Alternatively, if the Nexus 7 is on 3G, switch on its Wi-Fi hotspot and have the router/bridge connect to that.

I don't know if any commercially available special-purpose Wi-Fi routers have the ability to act as a client rather than an AP, but this would be easy to rig up with a Raspberry Pi or similar small Linux machine.