Two key points, IMHO, for a service to be fit for a SMS UI:

* Interaction sparsely needed.

* Usage where Internet access is either way too unreliable, and/or expensive (roaming? maybe offering different international numbers?)

Offtopic: Wait, Trondheim? Heihei, nabo :). Gløshaugen is killing me with exams, but let's have a beer some time.