[sevenaprils]

The 2008 Fit Sport Alloys contain electronic devices which monitor the tire pressure of each wheel (TPS) and send a signal to a unit built into the car's electronics' system. I haven't seen it, but I assume it will throw some sort of light sensor, probably the little maintenance minder wrench light.
In theory, you could probably take 2008 Sport alloys and put them on a 2007, since the older models don't have a TPS system, so the little devices in the wheels wouldn't affect anything. But, you wouldn't be able to do this with 07 rims transferred to an 08 unless you got a set of TPS units to put in each wheel - which would involve you needing to have your wheels removed, the units placed in each wheel, and then re-mounted. Probably by a Honda tech, just so it's installed properly.
If you have an 08, you can still get aftermarket wheels - just a little bit more work for where evere you get them installed since they'll have to get inside your stock sport alloys to get the sensors out and install them in the new aftermarket wheels. Just a slight PITA but easily resolved.
Gotta love when technology starts stepping on the fun modding factor of our cars...