apm install atom-bitcoin or search for
atom-bitcoin in Settings > Packages
This uses the BitcoinAverage API, an open source project designed to provide weighted average bitcoin price calculation. It utilises all exchanges where price and volume data is available.
Update interval defaults to 5 seconds but any second-based interval can be entered in the settings
Has colour updates to show increase/decrease/stable in price
Currency defaults to USD but any currency from the list below can be entered in the settings
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.