We used to use the Tommee Tippee Breathing monitor, but when DS went into his bed we had no choice but to stop using it as he could get out of bed himself (and therefore the breathing monitor would go off). He was 20 months, up until then I used the monitor religiously. We no longer bother even with the monitor (without the breathing monitor) until we go to bed and to be honest I think we only use it as we are used to the white noise of it (as we can hear DSs desktop fan through it - as well as him hehehehe). I find it too quiet to sleep with out it on once in our bedroom, even if DS jumps in bed with us or is staying at Nan's I still turn it on
Perhaps I just need to put a fan on in our own room then I can ditch it altogether