This document discusses the "Checkindj" project which uses check-ins on social networks to crowdsource music preferences in public spaces. It aims to allow groups of people to collectively influence and change the music played based on their check-ins. The system would use an online portal, music player, and RFID hardware to track check-ins and play appropriate music genres. An ethnography study is proposed to understand how the system impacts people's social experiences and perceptions of public spaces.