Create a graph of the free balance over time of a Substrate address
You can play with this app here: http://shawntabrizi.com/substrate-balance-graph/
Blog post: https://www.shawntabrizi.com/substrate/porting-web3-js-to-polkadot-js/
Built by repurposing: https://github.com/shawntabrizi/ethgraph