I guess if you look like you're on the way, and it looks like you're going to make it on time then it shouldn't prompt.

If you do get to the restaurant around the corner and stop then it should realise that it may need to remind you.

Anyway, I've signed up for it today. I like the idea in principle, and I understand how hard it is to get this right. I assume it will get better over time as they tweak it, so it's worth giving them a fair crack of the whip.