Between 1pm and 4pm tomorrow, you’ll be able to book an Audi R8 or a Hummer on your Uber app. The taxi aggregator has tied up with Droom, an online auto marketplace, which is providing the cars for this (highly) limited period. No details are available about exactly how many R8s and Hummers can be booked, but according to Droom you can get a ride free of cost. So bust out the app at the appropriate time tomorrow and try your luck.