Long time ago I was staying with one of my teachers. I heard very often some sound like "peep, peep", he then just touch something and after few minutes the sound was here again, and so on. I asked him "What is it?" and he replied: "This is a machine for realization". And he showed me small tea timer from his pocked. Without much of explanation I understood how it works: when the timer make a noise, you have to recolect your presence and awareness and continue in that as long, as you can.
So, recently I buy a machine for realization, very small timer which you can hide in the palm of your hand. It has also some pinze-nez from back side, so it can hold on your pocked hidden from sights of others. His sound is very gentle, not very loud. I set it up on 20 minutes and decided to come back every time from confusion to awareness. It work great, I could only recomend it for every urban yogi!