Repeating timer question

Device: Pebble Time

Goal:
No Bluetooth connection
Start a repeating timer (vibrate every 5mins)
By shortcut button (ie. Long press up)
Without leaving the watchface
Stop by same method.

Anyone have an Idea how to do this?
The only way I can think of is using Tasker (needs bluetooth) or using a timer app (leaves watchface to go to app).

Any help is much appreciated :)