I had two breaking attempts last year. After the first attempt, I had my landlord install better locks, and I also made my own security solution. Being in an apartment, I can't get a major brand alarm system (that comes with a three year contract)
So, I bought a Panasonic BL-C230A web camera. I made custom mobile page on a website, which I use to arm and disarm my "alarm". I've also setup the panasonic camera to visit a URL every time it detects motion. If the alarm is armed and it receives a visit on this URL, it will send me a text message and an email letting me know that it has detected motion. I also have it uploaded an image to an offsite FTP server whenever it records motion (which is somewhat bandwidth intensive). However, I can pull up a website and see every recent event that happened in my apartment.
I also contemplated using Tropo as an alerting system for phone and SMS. Doing so would even let me setup a call tree and all that. I never got around to implementing it but it seems like it would have worked well for this.
Also, I tried a D-Link model before the Panasonic webcam. The Panasonic ended up being the best camera for this solution though. The huge feature is the infrared motion sensor. Most webcams seem to detect motion by a determining a change in the image. However, if anything causes the change shift quickly, these give off a false positive. Which is not a great thing for an alarm to do several times a day. A few other nice features are the FTP capability, visiting a webpage when motion is detected, PTZ, and external inputs and outputs (for example, you could use these for a door open/close sensor or a siren).