Admozi
http://admozi.com/Digital Billboards Everywhere
Admozi is a location-aware mobile advertising platform, network and marketplace, it is currently in public beta. Admozi allows anyone to turn their phone, tablet or smart TV into a digital billboard and sell their screen space to the public. Advertisers compete in a real-time marketplace to place their ads either globally or to devices near a specific location. We also have an SDK for web sites and apps.
Angel list: https://angel.co/company/admozi