I think that it might be possible to turn an Arduino into a TellyMate with a few components and uploading an M168 version of the TellyMate firmware (as yet untested) onto the Arduino using its bootloader - I'm not sure of the command line options required to get avrdude to upload a generic .hex file to an Arduino though, but I believe it can be done. This 'TellyMate Arduino' wouldn't be able to do anything else except be a TellyMate though.
You'd therefore need a second Arduino to tell the first 'TellyMate arduino' what to display (unless a blinking cursor is all you want to show!) - Oh, and because the 'TellyMate Arduino' would still have a bootloader, you'd need to disconnect the 'TellyMate Arduino' before uploading any sketches to the second Arduino, otherwise they'll both attempt to receive the new sketch and things would get messy.
I'd try making a 'TellyMate Arduino' myself, except that my Arduino is a lowly M8, so the TellyMate firmware won't fit on it whilst there's a bootloader there.
[I hope that was understandable - on reading through again, it might be easier for The_Bongmaster to just buy/make a normal TellyMate!]
In the hope of keeping this thread 'News' like, here's a picture of the new version of the TellyMate Shield:
It's now got a 'professional' PCB, proper straight-through headers and can send back data to the Arduino.