Elbogrande, you are right for sure and that's probably exactly what I'll do is this case but the general problem is more tricky. I also have a two-volume dictionary to give my gran. I don't really want to mail that!
Myriam, I considered tickling it but that has obvious problems. Waiting for is a good shout. I suppose I could also put it on the agenda list and just ignore it if I'm on the phone. It seems like there are lots of ways to log this action in a GTD system but none of them are perfect. Maybe the folly is in striving for perfection when I could just log it somewhere (anywhere) and get on with cranking other widgets.