Breadcrumbs is a mobile app that "drops" virtual breadcrumbs while you're walking. Simply put, if you're walking from point A to point B, it stores information about HOW you got to point B, by keeping track of how many steps you took in every direction without using any internet. It uses smartphone’s pedometer, and magnetometer to record these “breadcrumbs”.
The direction information stored in each journey might be converted to Google Map instructions("Go straight 100 feet, then turn right etc...)