I just wanted to remind everyone that uses an angelcare monitor and has a fan on in their babies room to check that the monitor is not picking up vibrations from the fan. I had a fan on in Tori's room the other day and she was sick on her mattress, so I quickly lifted her and the mattress out without switching of the monitor, I didnt realise I hadnt switched off until a little bit later when I went back in to turn the fan off and the monitor went off 20 secs later.
So if you have a fan on in your babies room, just try turning the fan on and the monitor on without the baby in the cot to check that it is all ok.