Home security products are expensive and created by developers that have no interest in making things easy for end users. Instead, pull that old iPhone out of a drawer and make it the spy cam you've always wanted.
I have a few iPhones lying in drawers around my house. I should have sold them, but I didn't. After the recent thefts that took place in my garage, I've been contemplating getting a Wi-Fi enabled webcam that will upload photos. Then I realised I had exactly what I needed in an old iPhone.
iWebcam: Download iWebcam from the app store. Because your old phone probably can't handle iOS 5, or possibly even iOS 4, iWebcam is perfect. The app only requires iOS 3.1, so even your first generation iPhone can run the app.
Remember, thieves are in and out of a place in a matter of minutes. Set the photo interval to at the most 60 seconds. Set the app to record for a few days and remember to update the start and end time on a regular basis. No point in setting up a camera if it's not taking photos.
FTP or Email: The app saves photos to the iPhone's Photo Library, which will prove helpful after the fact. Or, you can email or FTP photos. If you choose email, be sure to create an account just for these emails. You can check on them periodically.
If you're lucky enough to have an FTP account, you can see the photos in a browser or FTP client without filling up an email account.
Mounting: Find a suitable area to mount the iPhone. Be sure the iPhone is pointed at an entrance area or towards items of value. From there, you have two choices. An overhead view of everything, or an eye-level view. Eye level will help police identify the thieves. Overhead will see more of what's going on.
If you've chosen eye level. Hide your iPhone inside something or it might end up being stolen along with your other items. Maybe stuff it in a book with a hole cut out, or inside a teddy bear -- like a nanny cam.
Power: iWebcam keeps your iPhone on all the time, so you'll need juice. Be sure to plug it in and set it to mute. The sound of your iPhone taking photos will probably be tip off to potential thieves.
Lighting: Photos of a dark room are worthless. Have a light with a motion sensor in the room you are watching. Not only will you see what's going on, but when you notice that photos begin arriving in your inbox that are brighter than usual, you can call the police to thwart the thieves.
Good ol' vigilante justice. It's like you're Batman without that whole murdered parents thing.