Hi Gracie, my dp's first son James died of sids at 9 weeks old, so he is fanatical about finding out all of the information that he can.
Sids for kids has a website with everything you need to know on it, just google sids for kids and it should be at the top.

The usual things that you can do to avoid it are,
Put baby to sleep on their back
Keep them away from ciggarette smoke
Make sure they're not too hot/cold
Just to name a few
I hope this helps
In reguards to the motion sensor pad, dp was adament he wanted one when i was pg with Nick, but we rang sids for kids and they said it can make you more paranoid because the alarms tend to go of quite frequently even if bub is ok, so we decided against it, but if you and DH think it will keep yor mind at ease then it might be ok for you, it comes down to individual choice.
I know it's hard but try not to worry to much about it, i did with my first pregnancy and it turned me into a wreck