I do buckle up, but when I want to, and if I'm going to drive 10 mph going downtown, I sometimes don't use the seat belt—irresponsible, I know.
Click here for the link to the extender for Honda Fits. Click here for link to seat belt extenders in general. The only caveat is that you have to depend upon the extender to be strong enough to not disconnect in an accident.
Now to figure out the keys-in-ignition/door-open bells, which I believe is more difficult.