Uber has an interesting offer for its carpool customers. It has launched a new feature called "Arrive By," which tells you the absolute latest time UberPOOL can take you to your destination. If you get there beyond the time it promised, you'll get $2 off your next UberPOOL trip, assuming you don't arrive so late you decide to swear off the service. You'll have to update your Uber app, select UberPOOL and type in your pick-up and drop-off locations to start seeing the estimates. The feature is only available in LA at the moment, but the company says it could be rolled out in additional markets.