Temporary Location Sharing App Idea

With virtually everyone carrying a GPS locating device at them at all times, it would be great to have an app where, for a discrete period of time, you could share your location with specific people.

This would be great for social events like pub crawling, where your group of friends could pick up their devices and see where their comrades are if they get separated.

Baked in functions:
Chat, for quick communication
Ability to temporarily suspend revealing your location for a certain amount of time
Notification when pre-defined time period of reveal or suspended location is ending to confirm the end. There should be an option to "snooze" the effect here too. (Keep revealing location to friends for a certain period, or keep suspending your location.
To save battery, the user could select how often they want for their location to be updated (at a period interval, or whenever another user opened the app to query their location).

The temporary nature of this is key, because after you leave the pub crawl, you don't need to be sharing your location anymore. (Or if you're too wasted to confirm the end of your location sharing, you friends can come find your body passed out in that alley.)