Just came across this app and it's quite nice! I've just shown it to my partner who's an occupational therapist, so she can hopefully use it with her clients.
There's two features I think would be useful (for me, at least)
1 - When setting a time-based limit, having an option for an alarm to go off would be useful. If I wanted to, say, meditate for 15 minutes then an alarm at the end of that 15 minutes would be useful. This wouldn't be as useful in the "goal" setting where you may not mind if you go over the defined time.
2 - When setting the period (ie. every day, every month, etc), a "custom" option would be great too. For example, I could do 15 minutes every 3 hours in between 9am and 6pm. Something like that would be great if I wanted to do 10 pushups 3 times a day, for example.
Lastly, this is more of a UI/UX enhancement, is to change the input type from NUM to TEL on any inputs that only require numbers (like inputting time periods). The keypad is easier to use on TEL in these cases.