What to do if your bike is stolen

Anyone here have the tech know how to do an App that all cyclists can have on their phones and report to the app a theft that will then alert all other cyclists within say 2 miles of where the theft took place. If anyone knows someone that can do that then maybe we could all contribute to such an app?
Just a though. I live in small village on south coast and even I have had bikes nicked from my garage nowhere is safe but when I get into london and see how many peletons of cyclist are out there I think an app would alert so many people that we could be catching them within minutes!

Check this out. http://www.thetileapp.com
It's called the tile and I think it's a really cool concept especially if everyone were to use it. I'm not sure how you could secure this onto a bike but they may make a down tube version?

Regards, MJ