What is the technology used in Note 3 coins identifier APP?

[AC Question]

I search a "coins identifier" on youtube and find the demonstration in Note 3 using Hong Kong Dollar.
However, there is no any download link of the APP or any explanation on how to make it. Anyone on know the technology behind?

 

[Rukbat]

I'm guessing it's the size of the coin. Or it could be a trick - the "coin ping" app sure is.