I would like you to fix the timer app:
The way I set a custom timer (and time in the alarm app) is painful. A way to set the selector for seconds to be 0/15/30/45, which I suspect are the most common cases. Perhaps in settings. Also for setting minutes some way to skip forward/back more quickly is also needed. Perhaps a two finger scroll for moving 5 unuits at a time?
Remember the last custom timer
Overall, might be better to have timer look like alarms with the values you have as presets and all off. A user can then change any of them or delete and add new ones to their liking. Likely be less code to maintain as well.