I made a simple script that monitors the Bitcoin price and does some silly notifications using light bulb flashes 
Video showcasing how it works: https://youtu.be/VvrtAw1AEcw
It uses the Bitcoin sensor for retrieving updated prices, and the scripts and templated that I made for it are here: https://pastebin.com/792dZhMY
Nice. Unfortunately the Bitcoin Sensor doesn’t work on my MHA (MacOS Home Assistant).
We made BitFetch and started using it with HA partly due to the unreliability of the Bitcoin sensor as well as the CoinMarketCap and other cryptocurrency HA sensors stopped working. We don’t have a custom component (yet!) but our team is successfully using it with HA in their homes via Node Red.
More info here: BitFetch.io - Integrate Bitcoin & Cryptocurrency Data into Home Assistant!
We’re happy to help you set it up if you need help, just DM us, and would love your feedback.