This is what it will do.
Every day, it will download and process the information for every TV channel I recieve, using XML-TV and store it in a website. It would then display this information and allow you to select items that you want to watch. So far, so normal.
Every five minutes, a cron job runs that checks to see if anything that anyone has registered as wanted to watch is going to start in the next five minutes. If so, it will send an email, or IM, or SMS to the person/s who requested such.
This will stop me missing Jonathan Creek and Walking With Cavemen every bloody time.