I have the angel care.. no they aren't neccesary but they are a great peace of mind.. I used to check my eldest a million times. I have had mine since my 2nd son and use it till they go into a bed..

I have the 2 mats, I don't think the Tommee Tippee one has 2 mats. I think single mat ones get more false alarms when baby gets bigger and starts moving around the cot..

Anyways personal opinion get the Angelcare if you choose to get one