useful app, useful marketing
It's really tough to create a mobile app meant to market your brand, but at the same time also be useful and/or entertaining enough to actually make people want to download it. This one, from Audi, brilliantly does both...
New Audi's now come with this smart, energy-saving technology that turns your engine off when not in use (like at a traffic light) and then back on when you accelerate. To get awareness out about this, Audi created a mobile application (called Start-Stop) that essentially does this same exact thing for your mobile phone battery, sending you alters to turn off apps running in the background for too long, etc.
Smart, strategic, simple.