I would go to your local police station and report it as suspious activity in the area. If somethng does happen later on to the car or a home break-in during the day there is already a report on file for them to reference. Most police departments will also start random patrols in the area or step up patrols. In addition you never know if they alreadyhave reports of similar activity or are looking for a similar vehicle in another part of town for similar activity.
If something does happen the first thing the police will ask is why you didnt report it. It will also help with any insurance claim that might be needed in the event of something happening that it was reported to police.
Just my two cents