The timer
A measurement in progress, visible everywhere, that you can finish or throw away.
Once started, the timer takes over the whole Add tab. The counter climbs by the second, the start time is recalled underneath, and two buttons are offered: finish, or cancel.
The banner, so you do not forget

As long as a measurement is running, a banner recalls it at the top of every page. The banner is itself the stop button. When a measurement has clearly overflowed, the application says so at the moment of recording rather than pretending nothing happened.
Finishing means landing on step two
Stopping the timer does not create an entry straight away. The measurement is set aside, the application offers the category list, and then shows the duration step with the measured minutes already filled in. Nothing is written until the entry is confirmed, and the proposed duration stays editable: a measurement of forty-seven minutes, seven of which were spent on the phone, can become forty.
Cancelling throws the measurement away and writes nothing.