Here's a purpose built Smart ForFour, carbon fiber widebody, roll cage, and a 2.0L 4 cylinder turbo engine producing 600hp. It looks like it loves the kitty litter.
The Insurance Institute for Highway Safety tested the Smart Fortwo and found that it protects it's passengers pretty well. Both front and side impact ratings are Good.
Since airbags, including the side curtain, are standard on Smart cars, they are safer and less expensive than a Toyota Yaris. $2730 or so will get you side airbags for the Yaris, it's free with a Smart.
Here is the first US television review of the 2008 Smart ForTwo. A Passion Coupe is reviewed, powered by a 1.0 liter dual cam 3 cylinder engine built by Mitsubishi.
The US model will come with front and side-impact airbags, driver's knee pad, and seatbelt tensioners as safety features.