duus,
I think that if it is going off every 15 minutes, you'll start to get used to it and ignore it after about an hour. It is like a pile of stuff on your desk; the longer you leave it there, the more you become used to it, and it stops bothering you as much.
I don't think this kind of hack works for mindfulness.
Try this: make a hipster PDA specifically as a food journal. Write what you ate, when, and how much. Do this dilligently for a few days. Look for patterns as to what triggers you to eat the wrong things.
As for the mindfulness... maybe some randomly placed (inside the medicine cabinet, on the foods you should cut back on, in your desk drawer at work, on the steering wheel...) stickie notes with positive messages, and reminders to breathe deeply might help out.
Just some thoughts,
Grieser