Modern mobile phones (cell phones) have predictive text input such as T9 or similar. This is quite nice, but there seems to be only one dictionary per language, and it makes general assumptions on what words are frequently used etc for the population as a whole.
It would be very nice to be able
to get a phone with a T9 dictionary more closely tailored to one's needs. Such as a "Language: Geek" or "Language: Skater" or perhaps for your mode of communication: "Language: Assertive", "Language: Passive-aggressive" etc.
Another great thing would be to have combo-dictionaries, for instance, choose to use both English and Swedish T9 dictionaries.
As far as I can see, T9 dictionaries are hardcoded into the actual phones as it is now. My idea would require downloadable dictionaries, or alternatively, that you could buy SIM-cards for various sub cultures and have the info on the card.