I just brought up my Google Location History screen to see what was new there. It does try to guess my travel mode now but it's very haphazard. It usually gets it that I was on a bike, but the beginning and end are terrible. I think the problem has something to do with trying to integrate wifi location, cell location and GPS so as an experiment I'm running it on GPS only.

It leads me to suspect, if Google can't get it right then there may be may be some technical challenges lurking under the surface for a software-only detection of a cycling trip. Or maybe it needs a more serious look than Google devoted to it - it's hard to tell with Google sometimes. Either way is not very encouraging.