Detecting a trip is easy - you're moving. But details and context. Google thinks I started when I rolled the bike out my front door and included coasting down the sidewalk, and that tying up the rack, walking through the parking garage and even up stairs is part of my cycling trip. In the google tracking context it's reasonable. It's all part of the trip that's best described as "cycling" and it's reasonable to include everything up to my ultimate destination. Google seems interested in the total time for a trip, among other aggregates. That doesn't really work though if you want precise metrics of the activity.

I still don't think it should be all that hard though. Even if I have to stop several times in the lot waiting for cars, and easing around children and dogs, I think an algorithm could determine just from motion that it was a bike, when you left the sidewalk, when you left the lot even. Add accelerometer data and it could be further refined.

It also seems to me that the app should also know what to do with it, within configurable parameters. Do I really want a trip to Best Buy loaded to Strava? Or seeing a medical specialist? Probably not but maybe I do want to tally that effort. Training ride or sprint intervals, maybe I do want to upload it. It would be useful if the app evaluated these things and took care of it.

I wouldn't want to waste time developing an android app if there's one already having a good subset of these features. It might in fact ultimately take more time than I'd ever save from not having to fumble with unnecessary user interfaces. But I don't see any insurmountable technical difficulty in what I want from it.