We also have the sensor pad with our DS. It has never gone off with a false alarm.

One other thing that I think is really important is don't use cot bumbers! The baby shops all have lovely displays with matching bedding and beautiful bumpers in the cots. They are just plain dangerous. Use a firm mattress that is the correct size for your cot, a fitted sheet and top sheet and blanket tucked in tightly away from babys face. For a new born that's about it, no soft toys, no sheets/blankets that aren't tucked in and definitely no bumpers!!