The Neighborhood I live in is looking at Security options. Ideally
battery powered wireless sensors could be put on existing mailbox
posts, and use a variety of sensor technologies whose information
would be captured into a database on a Community web site. Sensors
would track vehicles (perhaps other things) as they entered or exited
the two publicly maintained roads that lead into the neighborhood - as
well as at other street-intersection in the Neighborhood - and even
perhaps at driveway entrances. Ideally Lic Tag information could be
automatically captured and automatically compared with residents'
vehicles.  If not Lic Tags, then
parhaps active RFID could be used for positive automatic
identification of Vehicles that "belong" and those that are
questionable.

How close can I get to this using todays technology and without
needing a PHD in Electronic design (ie. spending way too much
money)and what are the products that that could be used?

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Clarification of Question by thehog-ga on 19 Apr 2006 16:53 PDT

The primary identifying information on a Lic Tag is the Lic Tag number
which connects the vehicle to its owner.

Also vehicle detection would probably best be handled from detecting
metal (magnetic) or weight (Pressure)- at least from what I know. 
Seems like Motion Detection would get everything and not just
vehicles.

I'm unsure what you're referring to when you say "Lic Tag"; could you elaborate?

In regards to using RFID, my guess is that you could stick a UHF tag
(typical range is 10-20 feet according to
http://www.rfidjournal.com/faq/18/69 ) in each car you're tracking,
and use a motion sensor to detect objects in the road.

A basic setup would involve a reader that would be triggered by the
motion sensor; if the reader doesn't recognize a known RFID sticker
carried by a car, then it would log an unknown passerby.

This kind of setup is going to be pretty tricky to use, given that
it's going to report a large number of incidents that'll turn out to
be the neighbourhood kids messing with the detector, or some animal in
the road. I'm not sure what kind of information you're wanting to
gather with this device, so maybe that's ok. I'd just be careful with
making judgements based on the stats the device reports.

Take a look at one of these RFID demo boards and play around with it
before you make a big decision:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Criteria?Ref=371521&Site=US&Cat=33686579

In regards to wirelessly reporting the logs, you could use a mesh
network running on 802.11g components if the devices are outdoors and
have a relative line of sight. Take a look at an evaluation kit from
here:http://www.lantronix.com/device-networking/embedded-device-servers/wiport.html#ordering

Writing a driver to link the wireless module together with the RFID
sensor might not be trivial though. Given that Lantronix seems to have
some experience doing this kind of thing
[http://www.lantronix.com/solutions/transportation.html] albeit for
larger organizations, they might be able to give you a hand.

[Note: I am in no ways affiliated with mentioned companies, and
haven't tried their products, so if you find something you're more
comfortable with, then go for it.]

I suppose the best detection for a vehicle would be a metal detector
instead of a traditional motion detector.

Also, to clarify on the Lic Tag ... to be able to automatically read
the tag number (OCR?) and compare it to all the Lic tags stored in the
Neighborhood database.  Obviously this would be best from a positive
ID standpoint.... In addition any vehicles that were not part of the
Neighborhood would be "logged" with a timestamp and could be useful
for police if needed.

I would rather not Invent this if something out there already exists or gets close.

http://www.digikey.com/scripts/DkSearch/dksus.dll?Criteria?Ref=371521&Site=US&Cat=33686579

Apparently this is a database or something ...that times out... I
could not get anything but a search page and a message about the data
set has expired ....

From the looks of the other references.... it looks like you are
saying that there isn't anything out there ... regarding RFID anyway.