Hi,
I would like to document my project and welcome any feedback.
I finally managed to get a TP-WR703N router bolted onto my Roomba but much to my frustration, these devices have very little flash memory (4MB!) so decided to develop a Roomba OI interpreter that would be web-aware, lean and easy to write code for.
I exhausted just about every option due to amount of flash and ram available so decided on Lua ( which I have no experience with) but is easy to embed in an openwrt firmware.
The project is still in the early stages but here is the progress so far...
Got a very basic web-interface running that provides access to basic remote control and running of custom LUA scripts.

Here are some views of the "brains" mounted on top... wish there was more room inside the roomba but this doesn't look too bad.



Finally a youtube vid of the first testing...
Update: 10.12.12
Still to do: Lots.... Lua socket daemon for HTML5 (for "instant" remote function). Lua editor front-end. Sound functions. Sensor definitions for Lua scripts. and much more.
Info on the hardware. The router is connected via the OI connector, there is an internal LM2596 DC converter wired up inside the roomba to supply 5v DC at the OI connector. A level shifter is inside the router casing (connected via /dev/ttyUSB0 at the moment, but will use internal tty connections once image is stable - thus freeing up the usb port for expansion... camera, flash, etc). Total cost of parts new (excluding Roomba) about $30.