There is a product from Mapzen that I have never seen anywhere else : Isochrones (https://mapzen.com/documentation/mobility/isochrone/api-refe...). Been interested in this for years (https://stackoverflow.com/questions/9403699/map-of-all-point...) They were the only ones to provide a solution.

I am super sad to see this go and still haven't seen any alternative.

Happy to hear about anything in this direction :s.

Thanks for mentioning this. Also keep in mind that mapzen its isochrone API:

as well as ours is open source: