On my pmDuo app, I noticed after a 10 mile cycle, pressing the record button to finish and save the cycle, and start the transition stage took a good few seconds where my watch doesn't respond. As I'd like to start recording the transition stage "immediately" after the cycle, it'd be nice to get over this hurdle.
I was wondering if there could be a way of speeding up the saving of Activity/FIT data, so I thought maybe the API could be changed so that you can call save() multiple times, with it writing unsaved changes to the end of the file.
That way, every mile or so, I could call save(), so when I reach the end of the cycle, save() should take less than a second before it starts up the next session
discard() can always delete the file if called.
Aside from the time benefits, I think it also would be great that if your watch ran out of battery part-way through your session, you'd still have a partial data file.