When would you call for help if someone was overdue?

Just about to spend three days doing selected sections of the Great Ocean Walk as day walks, with vehicle support, based at Apollo Bay in Victoria. Potentially dangerous coastline and I'm going to be doing it on my own, although I expect there will be lots of others on the track as it will be a long weekend for some.
Talking to my support team (my wife), we were discussing what to do if I didn't arrive to meet her by late afternoon. I mentioned that I would be leaving a trip intention form and route plan with local police, and that while she should warn police that I was late, she should not ask for help till the following morning when she came back and I was still not there.
What would you do?
For more resources on trip planning including trip intention forms, medical information forms and information on route cards http://www.bushwalkingskills.com/2010/09/planning-walk.html
Talking to my support team (my wife), we were discussing what to do if I didn't arrive to meet her by late afternoon. I mentioned that I would be leaving a trip intention form and route plan with local police, and that while she should warn police that I was late, she should not ask for help till the following morning when she came back and I was still not there.
What would you do?
For more resources on trip planning including trip intention forms, medical information forms and information on route cards http://www.bushwalkingskills.com/2010/09/planning-walk.html