Thoughts or Recommendations on Crib Breathing/Movement Monitors

Jenna - Baby boy born February 15, 2019

I've been looking into baby monitors and my mom is insisting that I get one that go under the mattress to detect breathing and sounds an alarm if movement/breathing stops for a certain period of time. Anyone have any thoughts on this or recommendations on what to get?

I'm getting overwhelmed by what to look for and what is worth it or not. Thanks in advance for any help!