Harry Potter fans may remember the Weasley's magical clock that always knows the location of family members.
via Harry Potter Wikia
Well, someone made a real life version of that clock. Using the GPS of his family's smartphones, Imgur user tbornottb was able to program the clock to light up when they reached different locations. Reading through the step by step process makes it seem almost easy. All it took was a whole lot of wires, lights, programming, app coordinating....
It was basically magic.
The result of all that work is a beautiful piece of technology and probably well worth it. Although it does carry the implication that your parents will know your location at all times...