I was wondering if anybody knows of any software for a computer that would use a webcam to monitor an area and tigger a DSLR to take a picture when motion is detected?
I'm using a Canon T2i and a windows 8 computer.
While this solution does not use a webcam, it does what you want.
The Magic Lantern custom firmware can be downloaded for free and includes, among many other interesting features, motion detection functionality.
It supports a wide range of Canon cameras, including the Canon T2i/550D.
You can attach any UVC-compliant web cam to a Linux computer (including a Raspberry Pi) and use the excellent Motion package to do the motion detection. It has the option to run a command when it sees motion, and you can set it up to call GPhoto2 and take a picture with your attached T2i.
The CameraAxe will let you trigger your camera from nearly anything, sound, light, lightening, movement, etc. Its available as a kit or completed.
While not using a webcam per se, the CHDK = Canon Hack Development Kit could be used for your task with relative ease.
On cameras which it works with, CHDK allows flexible control of all camera features.
CHDK can control just about any camera controllable feature and can output data on the USB port. This could be used with relatively simple hardware for camera control. CHDK allows eg defining a window within its view area and capturing images or performing other functions when motion is detected.
Using a CHDK equipped camera to trigger a DSLR flash:
There are many possible ways. Here are two -
(1) Use remote flash sensing trigger module on DSLR -
Trigger flash on CHDK camera to optically trigger DSLRs.
Can be arranged if desired so that CHDK camera flash does not illuminate main target.
(2) Obtain optocoupler requiring a few mA input current, bipolar or MOSFET transistor output. (1-5 mA best, 5-10 mA should be OK, much gigherworks but unneeded.
Place opto coupler input + resistor to suit desired current from USB+ to gnd on CHDK camera USB connection.
On motion detection, trigger initiate CHDK camera USB action - can be anything that toggles USB+. For opposite "sense" use USB- to ground.
Use opto output in any of the circuits available on web for camera triggering via external trigger socket. There are many and nominating any one is pointless. Opto ouput acts as a single pole single throw switch.