The world’s currencies (digital and physical) are only worth something because we all agreed that they are. Without this universal agreement, they are worth no more than the metals or paper they're made from. So why not also give them practical value? Practical currency is not a new thing. Anything from a bullet to a pill can form the basis of a currency. But I’m talking about coins that can generate power and be used as batteries, coins that can absorb and cleanse pollutants, detect toxins or contagions, or coins that gather and transmit useful weather or traffic data. Due to the wide-spread nature of coins in circulation, any practical value they might impart would be a boon to civilization. Here I explore some possible technologies that could function as useful currency.