Some airlines such as Alaska and Southwest already offer this but the pain is monitoring the drops for your fare class etc. If Google is automating that, then more power to them!
This is the kind of change that is not fun to learn the hard way.
[1] https://onemileatatime.com/alaska-airlines-price-guarantee-e... [2] https://www.alaskaair.com/content/deals/special-offers/price...
So never again Marriott and I'm booking my travels via Priceline.