Bitcoin Forum

Not a novel idea, but haven't seen an analysis using this method for the past Summer, so think it's worthwhile to take a look at:

https://thebitnote.com/a-note-on-calling-tops-in-bitcoin-with-google-trends/

Works decent for Bitcoin, and OK for Litecoin and Ethereum, though Ethereum has seen mostly consolidation over the period evaluated so trend reversal/market sentiment systems like this aren't as informative.