What an ignorant comparison. You're comparing the replacement of a roof to the death of a spouse. Cold calling from the obits is the same as ambulance chasing, plain and simple.
When grandpa dies and grandma is sitting with an insurance salesman 2 days later looking at burial plans she is not thinking rationally. She will make decisions that may not be in her best interest because she is still grieving her loss.
I think the more respectable thing to do would be to wait a couple of months and then go door knock her. Tell her you heard about her husband's passing and you're deeply sorry for her loss. Give her your business card and tell her if there is anything you can ever do for her then she can give you a call. That makes you look like a respectful professional, instead of an ambulance chasing, profiteering insurance salesman who is only looking to make his next buck, not improve the lives of his clients.
You are suggesting doing the same thing as others have suggested.. You are still working the Obit.(ambulance chasing according to you) The only disagreement is how long should an agent wait. (In other words, how far behind the ambulance you should follow - on its bumper or three blocks back)
I probably wouldn't call on the grieving widow, widower after only three weeks but would not hesitate to talk to the pallbearers after that period of time had elapsed.