My girlfriends Mum was hugely involved with SIDS prior to her passing away from a form of cancer about 5yrs ago...

She told me similar about monitoprs & those movement/breathing sleep devices as you've said Liz! They havent played any part in reducing SIDS.
She also explained that the majority of babies whom have passed away from SIDS have had breathing issues, or been resused in hospital at birth or between birth & being sent home.

I visited my friend who's inlaws had bought the breathing/movement thingy & it was like a clock ticking back & fourth & if the baby stopped moving/breathing an alarm went off, but the noise was annoying like a tap dripping & so after about 5 or 6 days they had removed it!

Zyon will be in a hammock in our room, but both the girls went straight into their own rooms & I have never used a monitor, I can easily hear when my babioes need me & I adhere by all the SIDS info, but I personall;y dont think a monitor or the other thing are necessities!!!