This script tracks the premium/discount of Bitcoin perpetual contracts at various exchanges.
The premium/discount is calculated against an index price. The index price is calculated from spot exchange prices and are weighted as follows:
Bitstamp:28,81%
Bittrex:5,5%
Coinbase: 38,07%
Gemini: 7,34%
Kraken: 20,28
The difference between this script and other available scripts, is that exciting script seems to only focus on one exchange. This script is also open source.