The second developer preview of OS X Mountain Lion, which seeded to developers on Saturday, introduced support for location-based reminders in the “Reminders” app. In developer preview 1, users could only create due date-based reminders.
Interestingly, it appears the Mac will track your location when connected to Wi-Fi and alert you when you arrive at the specified location, just like an iPhone would.
The reminders can also be synced over-the-air to iOS devices using iCloud. Thus, you can create a reminder from your computer, and then be reminded by your iPhone, when you arrive at your destination. I do not know about you, but I am personally looking forward to not walking all the way upstairs to track my iPhone or create a reminder before I forget what I needed to do.