My car is visible from the street too. I just lock it when I go inside.

Douchebaggery aside I have actually had my center caps stolen while my car is in my driveway and now have lock nuts on my wheels just in case but I don't suppose there is that much you can do. Make sure alarm is active etc and a car cover might not be a bad idea either.

Don't leave keys laying around in easy to reach places in your house, though I think I would rather have an intruder find my keys and peacefully leave rather than face a confrontation. It's all a very slim chance anyway I would think.

Also make sure you change your insurance policy, if you have it insured as being in secured parking then you will have issues if it's stolen from an accessible driveway.