Ask HN: Review the project idea for Android

I am thinking of doing some project on android platform. Right now, these are the thoughts on my mind. People carry smart-phones 24X7 with themselves so, there is a lot of scope for interaction between these devices (through wifi, bluetooth or whatever). For example, I may want to sync my device's music library with my friend's or I may just want to copy recently added pictures in my friend's device. So, I am thinking of developing some kind of back-end and interface to communicate with all the devices that are present in the range of my device. It will create opportunities for new apps that target sharing between mobile devices. What do you guys think of this? All suggestions are welcome.