First of all, thanks you for advancing some ideas regarding challenging some of the real world issues with GTD. You sound like someone who likes to pick at existing systems to improve them.... hope you don't blow a gasket in real-world law :) You have my sympathy in advance.
I get how you're pushing the limits of location-specific reminders. I think in a few years the killer app for this will materialize.
One thing i wanted to hear developed more was how you work such a tight calendering system around your method. I've had so much trouble over the years marrying GTD with a calendar. What do you do?