I would like to make a home security system which would upload images & audio when motion is senses. I have looked at a few usb options such as:
Oak_USB_Sensors
Go! Motion Sensor

I know I can use the webcam for motion detection as well however I would prefer something which does not keep the CPU running hot continuously, will work even in the dark & is more specific.

Regards,
Stefan

I can't access the second link although I did look at the first link.
Acording to the datasheet, the Oak Move motion detector behaves as an HID! So, it can be made to work with Linux fairly easily! You might have to experiment a little but it should be do-able!

Motion-detection requires CPU. Think about it: "Look at the picture, look at the recent pictures, has anything significant changed? [now define "significant"]. Then do this 30 times a second (or whatever your camera's FPS is set for).

No camera will work in the dark, they all need some "light" even if it is IR.

to what ?

Take a look at motion though. It's good.

Thanks for the replies.

I have used 'motion' however I am using an old 400MHz CPU + 256Mb memory as the webcam & file server. Motion detection seems to keep the CPU tied up. A USB IR motion detection device should bypass this and leave the PC free for compressing all the images into a time lapse video. I thought that the IR motion does work in the dark - our motion activated night light seems to work well enough at night. By "more specific" I mean that the webcam motion detection does get affected by other things such as shadows & changes in ambient light.

I might fall back to using webcam motion detection however I have found one other device as well:
http://www.kslemb.com/content/view/9/10/

I would like to make sure that the device I get can easily be used in a Bash shell script which can upload files to a offsite server before I send $$$.

Regards,
Stefan

There are two variants of that one. Glob-key behaves as a keyboard according to that description and is probably the better option. Glob-com uses the usb to serial approach which would need you to poll the device. It's your choice.
Passive Infrared motion sensors detect thermal energy emitted by warm bodied creatures. They will work in the dark, but you will still need light for the web-cam to record anything!

Curious to know if you got your USB motion detector working on Linux, and if so, how? I'd like to just be able to run get a motion-detector to trigger my SheevaPlug so that it can send me a SMS.

I ended up getting the GlobX device for US$55. Luckily they accepted Paypal. I had to use a Windows only utility once to program the device with a "Macro". Essentially it means you can program it to supply any key or key combination (ie Ctr-F11) which the device will then produce when it senses motion. Under Gnome or KDE this keyboard shortcut can then start the webcam script. My problem is that I want to implement this on a headless server and I have not tried to get working outside of a KDE. I will update this when I have it sorted out.

Regards,
Stefan

BTW Under KDE the way to add keyboard shortcuts is via "Settings->Computer Administration->Input Actions" then "New->Global Shortcut->Command/URL"

Yes, please let us know what you come up with. Using a plug computer, I'd be doing it as a remote server also. Inserting a 'key catch' statement into some code that is always listening would work, and would give you the capability to do fun stuff like only trigger events between certain times or after certain duration of inactivity.