ISO symbols are just in for the Smarts, release date of 2-29-8.
Insurance Services Office (ISO) is the industry group that tracks cost new, crash, theft, injury, frequency, and severity statistics on every make and model of vehicle on the road. Based on the stats, they assign each car a "Symbol", which is simply a number on a scale of about 1 to 27.
The higher the number, the higher the rates on the car, particularly the comprehensive (fire, theft, vandalism) and collision rates. Most, but not all companies, use ISO factors, or a tweaked variation of them.
ISO has assigned symbols since the late 50's, so the scale nowadays generally runs from 7 to 27.
On the 2008 list, the lowest cars carry a Symbol 7 and 8, and include stripped versions of Chevy and Ford trucks and low-end SUVs, base model Chrysler minivan, and the ilk.
The highest cars carry a Symbol 27, and include (no surprise) Jags, Lexus hybrid, high end BMWs, and the like.
(Not all 2008 models have been assigned symbols yet, so the list is incomplete, and doesnt' include Mercedes, for example. We don't generally get the complete list til mid-year.)
The Smarts have been assigned a symbol 13 for the cabrio, and a symbol 8 for the 2 door hatchback. (The Pure and the Passion are both counted as hatchbacks).
It is entirely possible for a symbol to be changed on a new make or a new model, once more of them hit the road and more reliable statistics start filtering in, but it is unusual, unless a car has really horrible "loss experience". The redesigned Chevy Cavalier a few years back was one of the more eye-popping instances of a symbol going through the roof. But generally, they stay they same, or only go up a notch, maybe two at most.
The closest comparable vehicles I can think of offhand are a Mazda Miata (symbols 13 & 15), and a Chevy Aveo (symbols 12, 14, and 16). That one's not really a fair comparison since it's a four door.