If you always had audio with your video playback, when the video froze you could detect a lack of audio (silence). There are several hardware boxes that radio stations use for dead-air alarms. Some of those boxes can call you when they detect silence.

I've never used it, but this free software seems to be able to do something similar by detecting audio silence (adjustable silence window, threshold levels).

http://pira.cz/show.asp?art=silence

The website states the software can:

Send alert email message (supports also SSL authentication)
Save actual screenshot (and optionally attach it to email)
Run application(s), play backup mp3 file(s)
Reboot/shutdown the system
Kill application(s)
Drive port pin
Send HTTP query (inform about the status on your web site)
Speak using the Windows SAPI
and more!


That would help with a freeze, but if you lost video and audio continued, you'd need another solution.