I would preffer if there would be following option for this integration:
At launch Momentum could automatically show the current runnig google calendar entry as the focus for today (and write the start and end time after the name). If there is no entry right now – it could sho the last or the next entry in the calender (the user should have the option to choose the behavior for that case).
After I check the current focus in momentum as done it schould be changed to the next entry in the calendar – like autofocus (and it doesn’t matter if the entry already ended or not in the calendar).
There should be an option to show a few next items as a list under the focus item, or just the focus.