Q: Why do we have to use Calendar or Reminder to receive notifications?
Short Answer: Because there is no other reasonable ways to set notifications from a widget.
Long Answer: Currently today widgets cannot access UIApplication instance which is necessary to set location notifications. ([UIApplication sharedInstance] does not work.) Thus, it is technically infeasible to set notifications without using Calendar or Reminder unless Apple provides a way to access UIApplication from widgets. One possible workaround is to use an external server and silent notifications. Actually some widgets do that. But it does not sound great for my server to handle a large amount of traffic from agents with iOS devices. If you know a way to set location notifications in widgets, please send me an email. I'm happy to add it to my code.
Q: Is there any plan to add more timers such as XM regeneration?
A: Yes. I'm going to add in-app purchase for additional features inlcuding more timers.