simple home monitoring?

[Tim Chase]

On July 18, 2015, Karen Lewellen wrote:
> Would be nice is a simple system that I can dedicate a machine for, 
> meaning a basic setup, with few resources required.
> perhaps software that would email me an alert  or monitoring
> results.

Depending on the complexity of the solution you want, and what you
have on hand, your solution can range from free-ish to several hundred
dollars.

At the cheapest end of the spectrum, if you already have a
computer/laptop with a camera (A generic USB web-cam should run under
$20 and I've spotted them for close to $5 on sale or used), as others
have mentioned, you can point the camera at the door and use some
vision-processing or motion-detection libraries to determine if the
camera sees movement. If so, this can trigger all manner of actions
(take a picture, send an email or text-message alert, sound alarms).
You could get false-alarms here though if you're not careful.  If you
monitor the entire frame that the camera captures, friends or dogs
walking around in the middle of the night might trigger alerts. You
might have to limit the observed area to the upper corner of the door
where it's unlikely to see motion you don't care about.  Also, it's
easy for a camera to get bumped unless you mount it on a wall.

A slight step up, some small hardware investment could put a
magnetic reed-switch (Adafruit sells one for $4) on your door-frame
and run a wire to something like a Raspberry Pi (another $30 for one
with a network jack on Adafruit) so that you capture door open/close
events and trigger an action only when the door really opens/closes.
You could even combine the ideas so that when the reed-switch detects
the door opening, an attached camera would take a picture/video and
upload it to an off-site location.  Or it could email you an alert or
play audio or whatever.  One of the biggest advantages of this setup
is how little power that the Pi draws.  A desktop/laptop may be
drawing 60-120 watts of power, whereas the Pi draw much less.  For a
security system that will be on all (or most of) the time, the
electricity costs can add up.

Finally at the mega-bucks end of the spectrum, you can get security
systems with multiple cameras, network integration, and alerts.
These are usually in the $300-1000 range depending on the number of
cameras and the features of the system.  This sounds like overkill
for what you want.  But maybe you won the lottery, in which case,
bully for you, knock yourself out and get a top-of-the-line system.
And fly me out as an installation consultant (grins)

-tim