This article is right on target:

A weblog is a record of travels on the Web, so a mobile phone log (moblog?) should be a record of travels in the world. Weblogs reflect our lives at our desks, on our computers, referencing mostly other flat pages, links between blocks of text. But mobile blogs should be far richer, fueled by multimedia, more intimate data and far- flung friends. As we chatter and text away, our phones could record and share the parts we choose: a walking, talking, texting, seeing record of our time around town, corrected and augmented by other mobloggers.

For a real-life example of this have a look at mark's picture log