Ride Auction allows you to Big & Ride on your price.  RideAuction was created by professionals in the ground transportation and technology industry to bring personal transportation companies together with customers via a competitive online and mobile auction platform. The result, is a bidding and auction service allowing RideAuction customers a new and exciting way to interactively negotiate the best possible rate for private transportation.  It's unique platform utilizes the idle time of our vendor’s fleet while allowing our customers to negotiate a fair price. 

They even go as far as to match you 110% if you find a cheaper deal online (conditions apply).  

With an App already in the Apple App Store available for download Ride Auction looks like a Startup that's off to a good start in disrupting the transportation space.  You can like them on facebook here.  Or show your support by following them on twitter.