What iphone app could snooze every 5 minutes? I hope to find an iphone app that remind me to focus, snooze every 5 minutes, can be configured to play a ringtone or just vibrate. If the "5 minutes" is configurable, that's even better.

Unfortunately iPhone Clock alarm snoozes every 10 minutes. and "Nag" application snoozes every 1 minute :(
Have you tried Due? It’s very configurable.
This link shows that after a reminder is triggered you can auto-snooze the notification in as low as 5 minute intervals.