Here's an augmented reality app that overlays live currency conversions on the foreign money in front of you.  Simply look at the money to see how much it's worth in the currency you're used to using.

There's a lot of ways this could be improved. It could add up all the money it can see, or it could simply re-skin the Danish Krone note to look like a dollar one, denoting the value. You see dollars, I see Krone. What matters is the exchange of value.

In this video I'm using the app with a pre-LiDAR iPhone, and I was surprised to see how well the virtual labels stick to the notes when I shake it.