It sounds like an extension of the T9 predictive text system present on every cell phone I've ever had. If so, it'll probably suffer the same difficulties: There are many more edge cases when you have fewer keys. Typing titles, acronyms and symbols all are painfully slow on T9, you have to click 3 or 4 times to get the desired character.
I think Dasher is more interesting. Not sure about the memory requirements, though.