Android Timer App Development

I need a minimalist Android app that prompts users to set a timer when switching to "vibrate" mode.

Features:
- Timer configuration:
- Select time via digital clock interface
- Choose duration with predefined options (15-min intervals, 1-hr intervals)
- Mix of common durations and custom options

- Popup window:
- Appears immediately after vibrate mode is activated
- Options to configure timer using either method
- Manual cancel option to switch ringer mode back to normal

- Notification bar display:
- Timer details (scheduled time, remaining time)
- Clickable to reopen timer popup with selected value

- Automatic return to "normal" ringer mode at scheduled time

Ideal skills and experience:
- Android app development
- Experience with notification management
- UI/UX design for minimalist interfaces